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+# Plans Library Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Let the app hold several named Macroplans in localStorage — switch between them, create and delete them, and download any plan as a portable `.toml` file.
+
+**Architecture:** `useMacroplan` becomes the owner of a `Library` (a `{version, activeId, plans[]}` object in localStorage), exposing the active plan's authoring state plus switch/create/delete operations. A new presentational `PlanSwitcher.vue` renders the header dropdown. A small `useSourceExport` util downloads the active plan's TOML, reusing a `slugify` helper extracted from the existing PNG exporter.
+
+**Tech Stack:** Vue 3 (`<script setup lang="ts">`), TypeScript, DaisyUI 5, `smol-toml` (already wired via `parseMacroplan`), Vitest + `@vue/test-utils` + happy-dom.
+
+**Spec:** `docs/superpowers/specs/2026-06-17-plans-library-design.md`
+
+## Global Constraints
+
+- Vue 3 `<script setup lang="ts">` for all components; match the existing component style.
+- DaisyUI 5 classes for UI (the app pins a light theme); no new dependencies.
+- No backend — everything client-side (ADR-0002). localStorage keys: **`macroplan:library`** (new store) and **`macroplan:source`** (legacy, single-source — migrate away from it).
+- Vitest defaults to the `node` environment; any test that touches the DOM or `localStorage` MUST start with the line `// @vitest-environment happy-dom` (see `src/components/MacroplanGrid.test.ts`).
+- Plan ids come from `crypto.randomUUID()`. Target is modern browsers; no fallback.
+- A plan's display **name** is its parsed TOML `title` (cached as last-good); it is **not** a separately edited field.
+- **Invariant:** the library always holds ≥ 1 plan.
+- Conventional-commit messages, lowercase, imperative. **Do NOT add `Co-authored-by` lines** (user's standing rule).
+- Run a single test file with `pnpm exec vitest run <path>`; full suite with `pnpm test`; typecheck + build with `pnpm build`.
+
+---
+
+### Task 1: TOML filename helpers + `downloadSource`
+
+Extract a reusable `slugify` from the PNG exporter and add a `.toml` filename + download utility. Foundational and dependency-free.
+
+**Files:**
+- Modify: `src/composables/usePngExport.ts` (extract `slugify`, keep `exportFilename` output identical)
+- Create: `src/composables/useSourceExport.ts`
+- Test: `src/composables/useSourceExport.test.ts`
+- (Unchanged, must still pass: `src/composables/usePngExport.test.ts`)
+
+**Interfaces:**
+- Produces: `slugify(title: string): string` (exported from `usePngExport.ts`) — lowercased, non-alphanumerics collapsed to dashes, edge dashes trimmed, **no** extension and **no** `plan` fallback.
+- Produces: `sourceFilename(title: string): string` → `macroplan-<slug-or-plan>.toml`
+- Produces: `downloadSource(source: string, filename: string): void`
+
+- [ ] **Step 1: Write the failing test**
+
+Create `src/composables/useSourceExport.test.ts`:
+
+```ts
+import { describe, it, expect } from 'vitest'
+import { sourceFilename } from './useSourceExport'
+
+describe('sourceFilename', () => {
+  it('slugifies the plan title into a .toml name', () => {
+    expect(sourceFilename('Q3 — Checkout revamp')).toBe('macroplan-q3-checkout-revamp.toml')
+  })
+
+  it('falls back to a generic name when the title has no usable characters', () => {
+    expect(sourceFilename('')).toBe('macroplan-plan.toml')
+    expect(sourceFilename('—— ··')).toBe('macroplan-plan.toml')
+  })
+})
+```
+
+- [ ] **Step 2: Run the test to verify it fails**
+
+Run: `pnpm exec vitest run src/composables/useSourceExport.test.ts`
+Expected: FAIL — cannot resolve `./useSourceExport`.
+
+- [ ] **Step 3: Extract `slugify` in `usePngExport.ts`**
+
+Replace the existing `exportFilename` function (lines 5–13) with:
+
+```ts
+/** Lowercase, dash-collapsed slug of a plan title — no extension, no fallback. */
+export function slugify(title: string): string {
+  return title
+    .toLowerCase()
+    .trim()
+    .replace(/[^a-z0-9]+/g, '-')
+    .replace(/^-+|-+$/g, '')
+}
+
+/** Slugified, stable download name derived from the plan title. */
+export function exportFilename(title: string): string {
+  return `macroplan-${slugify(title) || 'plan'}.png`
+}
+```
+
+- [ ] **Step 4: Create `useSourceExport.ts`**
+
+```ts
+import { slugify } from './usePngExport'
+
+/** Slugified, stable download name for a plan's TOML source. */
+export function sourceFilename(title: string): string {
+  return `macroplan-${slugify(title) || 'plan'}.toml`
+}
+
+/** Download a plan's TOML source as a .toml file (client-side, no backend). */
+export function downloadSource(source: string, filename: string): void {
+  const blob = new Blob([source], { type: 'text/plain;charset=utf-8' })
+  const url = URL.createObjectURL(blob)
+  const a = document.createElement('a')
+  a.href = url
+  a.download = filename
+  a.click()
+  URL.revokeObjectURL(url)
+}
+```
+
+- [ ] **Step 5: Run both filename test files to verify they pass**
+
+Run: `pnpm exec vitest run src/composables/useSourceExport.test.ts src/composables/usePngExport.test.ts`
+Expected: PASS (both files; the existing `exportFilename` tests still pass because output is unchanged).
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add src/composables/usePngExport.ts src/composables/useSourceExport.ts src/composables/useSourceExport.test.ts
+git commit -m "feat(export): add .toml source download and shared slugify helper"
+```
+
+---
+
+### Task 2: `PlanSwitcher.vue` (presentational dropdown)
+
+A header dropdown that lists plans, marks the active one, and emits switch / new / download intents. No storage or parsing logic — props in, events out.
+
+**Files:**
+- Create: `src/components/PlanSwitcher.vue`
+- Test: `src/components/PlanSwitcher.test.ts`
+
+**Interfaces:**
+- Consumes: nothing from other tasks.
+- Produces: component `PlanSwitcher` with
+  - Props: `plans: { id: string; name: string }[]`, `activeId: string`
+  - Emits: `select: [id: string]`, `new: []`, `download: [id: string]`
+  - DOM contract relied on by the test: each plan is an `<a>` inside a `<li>`; the active plan's `<a>` has class `active`; the last two `<a>` items are **New plan** then **Download .toml**.
+
+- [ ] **Step 1: Write the failing test**
+
+Create `src/components/PlanSwitcher.test.ts`:
+
+```ts
+// @vitest-environment happy-dom
+import { describe, it, expect } from 'vitest'
+import { mount } from '@vue/test-utils'
+import PlanSwitcher from './PlanSwitcher.vue'
+
+const plans = [
+  { id: 'a', name: 'Alpha' },
+  { id: 'b', name: 'Bravo' },
+]
+
+describe('PlanSwitcher', () => {
+  it('lists plan names and marks the active one', () => {
+    const w = mount(PlanSwitcher, { props: { plans, activeId: 'b' } })
+    expect(w.text()).toContain('Alpha')
+    expect(w.text()).toContain('Bravo')
+    expect(w.find('a.active').text()).toContain('Bravo')
+  })
+
+  it('emits select with the clicked plan id', async () => {
+    const w = mount(PlanSwitcher, { props: { plans, activeId: 'a' } })
+    await w.findAll('li a')[1].trigger('click') // Bravo
+    expect(w.emitted('select')?.[0]).toEqual(['b'])
+  })
+
+  it('emits new and download (with the active id) from the trailing actions', async () => {
+    const w = mount(PlanSwitcher, { props: { plans, activeId: 'a' } })
+    const actions = w.findAll('li a')
+    await actions[actions.length - 2].trigger('click') // New plan
+    await actions[actions.length - 1].trigger('click') // Download .toml
+    expect(w.emitted('new')).toBeTruthy()
+    expect(w.emitted('download')?.[0]).toEqual(['a'])
+  })
+})
+```
+
+- [ ] **Step 2: Run the test to verify it fails**
+
+Run: `pnpm exec vitest run src/components/PlanSwitcher.test.ts`
+Expected: FAIL — cannot resolve `./PlanSwitcher.vue`.
+
+- [ ] **Step 3: Create `PlanSwitcher.vue`**
+
+```vue
+<script setup lang="ts">
+import { computed } from 'vue'
+
+const props = defineProps<{
+  plans: { id: string; name: string }[]
+  activeId: string
+}>()
+
+const emit = defineEmits<{
+  select: [id: string]
+  new: []
+  download: [id: string]
+}>()
+
+const activeName = computed(
+  () => props.plans.find((p) => p.id === props.activeId)?.name ?? 'Untitled',
+)
+</script>
+
+<template>
+  <div class="dropdown">
+    <div tabindex="0" role="button" class="btn btn-ghost btn-sm gap-1 normal-case">
+      <span class="max-w-[14rem] truncate font-semibold">{{ activeName }}</span>
+      <span aria-hidden="true">▾</span>
+    </div>
+    <ul
+      tabindex="0"
+      class="menu dropdown-content z-50 mt-1 w-64 rounded-box border border-base-300 bg-base-100 p-2 shadow-lg"
+    >
+      <li v-for="p in plans" :key="p.id">
+        <a :class="{ active: p.id === activeId }" @click="emit('select', p.id)">
+          <span class="truncate">{{ p.name }}</span>
+          <span v-if="p.id === activeId" aria-hidden="true">✓</span>
+        </a>
+      </li>
+      <div class="my-1 border-t border-base-200"></div>
+      <li><a @click="emit('new')">＋ New plan</a></li>
+      <li><a @click="emit('download', activeId)">⤓ Download .toml</a></li>
+    </ul>
+  </div>
+</template>
+```
+
+- [ ] **Step 4: Run the test to verify it passes**
+
+Run: `pnpm exec vitest run src/components/PlanSwitcher.test.ts`
+Expected: PASS (3 tests).
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add src/components/PlanSwitcher.vue src/components/PlanSwitcher.test.ts
+git commit -m "feat(ui): add the plan switcher dropdown"
+```
+
+---
+
+### Task 3: `useMacroplan` library refactor
+
+Turn the single-source composable into the Library owner: storage + migration + active-plan binding + autosave, plus the switch/create/delete operations. Keep `resetToSample` exported for now so `App.vue` still compiles — Task 4 removes it.
+
+**Files:**
+- Modify (rewrite): `src/composables/useMacroplan.ts`
+- Test: `src/composables/useMacroplan.test.ts`
+
+**Interfaces:**
+- Consumes: `parseMacroplan` (throws `PlanParseError`; defaults `title` to `'Untitled Macroplan'`), `buildPlan`, `SAMPLE_PLAN` (its title is `"Q3 — Checkout revamp"`).
+- Produces (the composable's return shape, relied on by Task 4):
+  - `source: WritableComputedRef<string>` — reads/writes the active plan's source
+  - `plan: ComputedRef<Plan | null>`
+  - `error: ComputedRef<string | null>`
+  - `plans: ComputedRef<{ id: string; name: string }[]>`
+  - `activeId: ComputedRef<string>`
+  - `selectPlan(id: string): void`
+  - `newPlan(): void`
+  - `deletePlan(id: string): void`
+  - `resetToSample(): void` *(temporary — removed in Task 4)*
+
+- [ ] **Step 1: Write the failing tests (storage, binding, CRUD)**
+
+Create `src/composables/useMacroplan.test.ts`:
+
+```ts
+// @vitest-environment happy-dom
+import { describe, it, expect, beforeEach } from 'vitest'
+import { nextTick } from 'vue'
+import { useMacroplan } from './useMacroplan'
+import { SAMPLE_PLAN } from '../data/sample'
+
+const LIB_KEY = 'macroplan:library'
+const LEGACY_KEY = 'macroplan:source'
+
+beforeEach(() => localStorage.clear())
+
+describe('useMacroplan — load & migration', () => {
+  it('seeds one sample plan when storage is empty, and persists it immediately', () => {
+    const m = useMacroplan()
+    expect(m.plans.value).toHaveLength(1)
+    expect(m.activeId.value).toBe(m.plans.value[0].id)
+    expect(m.source.value).toBe(SAMPLE_PLAN)
+    expect(localStorage.getItem(LIB_KEY)).toBeTruthy() // survives a reload
+  })
+
+  it('migrates a legacy single-source store into a one-plan library and drops the legacy key', () => {
+    localStorage.setItem(LEGACY_KEY, SAMPLE_PLAN)
+    const m = useMacroplan()
+    expect(m.plans.value).toHaveLength(1)
+    expect(m.source.value).toBe(SAMPLE_PLAN)
+    expect(m.plans.value[0].name).toBe('Q3 — Checkout revamp')
+    expect(localStorage.getItem(LEGACY_KEY)).toBeNull()
+  })
+
+  it('falls back to a fresh sample when the library JSON is corrupt', () => {
+    localStorage.setItem(LIB_KEY, '{ not valid json')
+    const m = useMacroplan()
+    expect(m.plans.value).toHaveLength(1)
+    expect(m.source.value).toBe(SAMPLE_PLAN)
+  })
+
+  it('repairs a stale activeId instead of discarding the stored plans', () => {
+    localStorage.setItem(
+      LIB_KEY,
+      JSON.stringify({
+        version: 1,
+        activeId: 'gone',
+        plans: [{ id: 'x', name: 'Kept', source: SAMPLE_PLAN }],
+      }),
+    )
+    const m = useMacroplan()
+    expect(m.activeId.value).toBe('x')
+    expect(m.plans.value[0].name).toBe('Kept')
+  })
+})
+
+describe('useMacroplan — active plan binding', () => {
+  it('refreshes the cached name when the active source parses to a title, and autosaves', async () => {
+    const m = useMacroplan()
+    m.source.value = 'title = "Renamed"\n'
+    await nextTick()
+    expect(m.plans.value[0].name).toBe('Renamed')
+    expect(localStorage.getItem(LIB_KEY)).toContain('Renamed')
+  })
+
+  it('keeps the last-good name and render when the source is mid-edit/broken', async () => {
+    const m = useMacroplan()
+    const goodPlan = m.plan.value
+    m.source.value = 'title = "Renamed"\n[[feature]]\n' // feature missing name → parse error
+    await nextTick()
+    expect(m.error.value).toBeTruthy()
+    expect(m.plan.value).toBe(goodPlan) // last-good render retained
+    expect(m.plans.value[0].name).toBe('Q3 — Checkout revamp') // name unchanged
+  })
+})
+
+describe('useMacroplan — CRUD', () => {
+  it('newPlan appends a sample plan and activates it', () => {
+    const m = useMacroplan()
+    const firstId = m.activeId.value
+    m.newPlan()
+    expect(m.plans.value).toHaveLength(2)
+    expect(m.activeId.value).not.toBe(firstId)
+    expect(m.source.value).toBe(SAMPLE_PLAN)
+  })
+
+  it('deletePlan removes the active plan and re-points to the preceding one', () => {
+    const m = useMacroplan()
+    m.newPlan() // 2 plans; second is active
+    const [first, second] = m.plans.value
+    m.deletePlan(second.id)
+    expect(m.plans.value).toHaveLength(1)
+    expect(m.activeId.value).toBe(first.id)
+  })
+
+  it('deleting the last plan re-seeds a fresh sample (never empty)', () => {
+    const m = useMacroplan()
+    m.deletePlan(m.activeId.value)
+    expect(m.plans.value).toHaveLength(1)
+    expect(m.source.value).toBe(SAMPLE_PLAN)
+  })
+
+  it('switching to a broken plan shows its own empty state, not the previous render', async () => {
+    const m = useMacroplan()
+    const aId = m.activeId.value
+    m.newPlan()
+    const bId = m.activeId.value
+    m.source.value = 'title = "B"\n[[feature]]\n' // B broken
+    await nextTick()
+    m.selectPlan(aId)
+    await nextTick()
+    expect(m.plan.value).toBeTruthy() // A renders
+    m.selectPlan(bId)
+    await nextTick()
+    expect(m.error.value).toBeTruthy() // B's parse error surfaces
+    expect(m.plan.value).toBeNull() // no stale A render leaks through
+  })
+})
+```
+
+- [ ] **Step 2: Run the tests to verify they fail**
+
+Run: `pnpm exec vitest run src/composables/useMacroplan.test.ts`
+Expected: FAIL — the new API (`plans`, `activeId`, `newPlan`, etc.) does not exist yet.
+
+- [ ] **Step 3: Rewrite `useMacroplan.ts`**
+
+Replace the entire file with:
+
+```ts
+import { ref, computed, watch } from 'vue'
+import { parseMacroplan } from '../model/parse'
+import { buildPlan } from '../model/plan'
+import type { Plan } from '../model/types'
+import { SAMPLE_PLAN } from '../data/sample'
+
+const STORAGE_KEY = 'macroplan:library'
+const LEGACY_KEY = 'macroplan:source'
+
+export interface StoredPlan {
+  id: string
+  name: string
+  source: string
+}
+
+interface Library {
+  version: 1
+  activeId: string
+  plans: StoredPlan[]
+}
+
+/** The source's title if it fully parses, else null (so the cached name only
+ *  ever updates on a valid parse). */
+function titleOf(source: string): string | null {
+  try {
+    return parseMacroplan(source).title
+  } catch {
+    return null
+  }
+}
+
+function newStoredPlan(source: string): StoredPlan {
+  return { id: crypto.randomUUID(), name: titleOf(source) ?? 'Untitled', source }
+}
+
+function save(lib: Library): void {
+  try {
+    localStorage.setItem(STORAGE_KEY, JSON.stringify(lib))
+  } catch {
+    /* localStorage may be full or blocked — autosave is best-effort */
+  }
+}
+
+/** Resolve the initial library: existing store → legacy migration → fresh seed.
+ *  Always persisted before returning so a migrated/seeded library survives a
+ *  reload even if the user never edits. */
+function loadLibrary(): Library {
+  let result: Library | null = null
+
+  const raw = localStorage.getItem(STORAGE_KEY)
+  if (raw) {
+    try {
+      const lib = JSON.parse(raw) as Library
+      if (lib && Array.isArray(lib.plans) && lib.plans.length > 0) {
+        if (!lib.plans.some((p) => p.id === lib.activeId)) lib.activeId = lib.plans[0].id
+        result = { version: 1, activeId: lib.activeId, plans: lib.plans }
+      }
+    } catch {
+      /* corrupt JSON → fall through to migration / seed */
+    }
+  }
+
+  if (!result) {
+    const legacy = localStorage.getItem(LEGACY_KEY)
+    if (legacy != null) {
+      const p = newStoredPlan(legacy)
+      localStorage.removeItem(LEGACY_KEY)
+      result = { version: 1, activeId: p.id, plans: [p] }
+    } else {
+      const seed = newStoredPlan(SAMPLE_PLAN)
+      result = { version: 1, activeId: seed.id, plans: [seed] }
+    }
+  }
+
+  save(result)
+  return result
+}
+
+/**
+ * Owns the Library — the collection of named Macroplans in localStorage
+ * (ADR-0002). Exposes the active plan's authoring state (source / parsed plan /
+ * error, with the last good render kept through transient typos, F3) plus the
+ * switch / create / delete operations over the library.
+ */
+export function useMacroplan() {
+  const lib = ref<Library>(loadLibrary())
+  const lastGood = ref<Plan | null>(null)
+
+  const active = computed<StoredPlan>(
+    () => lib.value.plans.find((p) => p.id === lib.value.activeId) ?? lib.value.plans[0],
+  )
+
+  const source = computed<string>({
+    get: () => active.value.source,
+    set: (v) => {
+      const p = active.value
+      p.source = v
+      const t = titleOf(v)
+      if (t) p.name = t // refresh the cached label only on a valid parse
+    },
+  })
+
+  const parsed = computed<{ plan: Plan | null; error: string | null }>(() => {
+    try {
+      return { plan: buildPlan(parseMacroplan(source.value)), error: null }
+    } catch (e) {
+      return { plan: null, error: e instanceof Error ? e.message : String(e) }
+    }
+  })
+
+  watch(
+    parsed,
+    (p) => {
+      if (p.plan) lastGood.value = p.plan
+    },
+    { immediate: true },
+  )
+
+  // Persist the whole library on any change (best-effort, like the old autosave).
+  watch(lib, (l) => save(l), { deep: true })
+
+  // Switching plans drops the prior render so a broken target shows its own
+  // error/empty state, not the previous plan's grid.
+  function switchTo(id: string): void {
+    lib.value.activeId = id
+    lastGood.value = parsed.value.plan
+  }
+
+  return {
+    source,
+    plan: computed(() => parsed.value.plan ?? lastGood.value),
+    error: computed(() => parsed.value.error),
+    plans: computed(() => lib.value.plans.map((p) => ({ id: p.id, name: p.name }))),
+    activeId: computed(() => lib.value.activeId),
+    selectPlan: (id: string) => {
+      if (lib.value.plans.some((p) => p.id === id)) switchTo(id)
+    },
+    newPlan: () => {
+      const p = newStoredPlan(SAMPLE_PLAN)
+      lib.value.plans.push(p)
+      switchTo(p.id)
+    },
+    deletePlan: (id: string) => {
+      const idx = lib.value.plans.findIndex((p) => p.id === id)
+      if (idx === -1) return
+      const wasActive = lib.value.activeId === id
+      lib.value.plans.splice(idx, 1)
+      if (lib.value.plans.length === 0) {
+        const seed = newStoredPlan(SAMPLE_PLAN)
+        lib.value.plans.push(seed)
+        switchTo(seed.id)
+      } else if (wasActive) {
+        switchTo(lib.value.plans[Math.max(0, idx - 1)].id)
+      }
+    },
+    // TODO(task 4): remove once App.vue drops the "Reset to sample" button.
+    resetToSample: () => {
+      source.value = SAMPLE_PLAN
+    },
+  }
+}
+```
+
+- [ ] **Step 4: Run the tests to verify they pass**
+
+Run: `pnpm exec vitest run src/composables/useMacroplan.test.ts`
+Expected: PASS (all groups).
+
+- [ ] **Step 5: Confirm the app still typechecks (App.vue unchanged, `resetToSample` retained)**
+
+Run: `pnpm build`
+Expected: build succeeds (no type errors).
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add src/composables/useMacroplan.ts src/composables/useMacroplan.test.ts
+git commit -m "feat(model): make useMacroplan own a library of named plans"
+```
+
+---
+
+### Task 4: Wire `App.vue` (switcher, delete confirm, .toml download)
+
+Replace the static title block with the switcher, add a trash button + confirm modal that deletes the active plan, wire the `.toml` download, and remove the now-retired `resetToSample`.
+
+**Files:**
+- Modify (rewrite): `src/App.vue`
+- Modify: `src/composables/useMacroplan.ts` (delete the temporary `resetToSample`)
+
+**Interfaces:**
+- Consumes: `useMacroplan` (`source`, `plan`, `error`, `plans`, `activeId`, `selectPlan`, `newPlan`, `deletePlan`), `PlanSwitcher`, `sourceFilename` + `downloadSource`, `exportFilename` + `usePngExport`.
+
+- [ ] **Step 1: Remove the temporary `resetToSample` from `useMacroplan.ts`**
+
+Delete these lines from the returned object:
+
+```ts
+    // TODO(task 4): remove once App.vue drops the "Reset to sample" button.
+    resetToSample: () => {
+      source.value = SAMPLE_PLAN
+    },
+```
+
+- [ ] **Step 2: Rewrite `App.vue`**
+
+Replace the entire file with:
+
+```vue
+<script setup lang="ts">
+import { ref, computed } from 'vue'
+import { useMacroplan } from './composables/useMacroplan'
+import { usePngExport, exportFilename } from './composables/usePngExport'
+import { sourceFilename, downloadSource } from './composables/useSourceExport'
+import PlanEditor from './components/PlanEditor.vue'
+import MacroplanGrid from './components/MacroplanGrid.vue'
+import PlanSwitcher from './components/PlanSwitcher.vue'
+
+const { source, plan, error, plans, activeId, selectPlan, newPlan, deletePlan } = useMacroplan()
+const { busy, toast, copyPng, downloadPng } = usePngExport()
+
+const exportRoot = ref<HTMLElement>()
+const confirmingDelete = ref(false)
+
+const activeName = computed(
+  () => plans.value.find((p) => p.id === activeId.value)?.name ?? 'Untitled',
+)
+
+function downloadToml() {
+  downloadSource(source.value, sourceFilename(plan.value?.title ?? activeName.value))
+}
+
+function confirmDelete() {
+  deletePlan(activeId.value)
+  confirmingDelete.value = false
+}
+</script>
+
+<template>
+  <div class="flex h-screen flex-col bg-base-200 font-sans text-base-content">
+    <header class="navbar min-h-0 gap-2 border-b border-base-300 bg-base-100 px-4 py-2">
+      <img src="/favicon.svg" alt="" class="size-6" />
+      <div class="flex-1">
+        <PlanSwitcher
+          :plans="plans"
+          :active-id="activeId"
+          @select="selectPlan"
+          @new="newPlan"
+          @download="downloadToml"
+        />
+      </div>
+      <button
+        class="btn btn-ghost btn-sm"
+        :disabled="!plan || busy"
+        title="Copy the rendered plan to the clipboard as a PNG"
+        @click="copyPng(exportRoot)"
+      >
+        <span v-if="busy" class="loading loading-spinner loading-xs"></span>
+        Copy PNG
+      </button>
+      <button
+        class="btn btn-ghost btn-sm"
+        :disabled="!plan || busy"
+        title="Download the rendered plan as a PNG"
+        @click="downloadPng(exportRoot, exportFilename(plan?.title ?? ''))"
+      >
+        Download
+      </button>
+      <button class="btn btn-ghost btn-sm" title="Delete this plan" @click="confirmingDelete = true">
+        🗑
+      </button>
+    </header>
+
+    <main class="flex min-h-0 flex-1 flex-col md:flex-row">
+      <section
+        class="flex min-h-0 flex-col border-base-300 max-md:h-2/5 max-md:border-b md:w-1/3 md:max-w-md md:border-r"
+      >
+        <div class="px-4 py-2 text-xs font-semibold uppercase tracking-wide text-base-content/50">
+          Source (TOML)
+        </div>
+        <PlanEditor v-model="source" :error="error" class="min-h-0 flex-1" />
+      </section>
+
+      <section class="min-h-0 flex-1 overflow-auto p-4">
+        <div v-if="plan" ref="exportRoot" class="export-root">
+          <h2 class="mb-3 text-sm font-semibold text-base-content/70">{{ plan.title }}</h2>
+          <MacroplanGrid :plan="plan" />
+        </div>
+        <p v-else class="text-sm text-base-content/60">
+          Nothing to render yet — fix the source on the left.
+        </p>
+      </section>
+    </main>
+
+    <dialog class="modal" :class="{ 'modal-open': confirmingDelete }">
+      <div class="modal-box">
+        <h3 class="text-base font-semibold">Delete “{{ activeName }}”?</h3>
+        <p class="py-2 text-sm text-base-content/70">
+          This removes the plan from your library. Download its .toml first if you want to keep it.
+        </p>
+        <div class="modal-action">
+          <button class="btn btn-sm" @click="confirmingDelete = false">Cancel</button>
+          <button class="btn btn-sm btn-error" @click="confirmDelete">Delete</button>
+        </div>
+      </div>
+      <form method="dialog" class="modal-backdrop" @click="confirmingDelete = false">
+        <button>close</button>
+      </form>
+    </dialog>
+
+    <div v-if="toast" class="toast toast-end">
+      <div class="alert" :class="toast.kind === 'ok' ? 'alert-success' : 'alert-error'">
+        <span>{{ toast.text }}</span>
+      </div>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+/* While exporting, grow to the timeline's full width and un-clip the grid so the
+   captured PNG shows every week column (not just the on-screen scroll window).
+   The base-200 frame + padding give the snapshot a little breathing room. */
+.export-root.exporting {
+  width: max-content;
+  padding: 1rem 1.25rem;
+  background: var(--color-base-200);
+}
+.export-root.exporting :deep(.macroplan) {
+  overflow: visible;
+}
+</style>
+```
+
+- [ ] **Step 3: Typecheck + build**
+
+Run: `pnpm build`
+Expected: build succeeds — no reference to `resetToSample` remains, all props/events typecheck.
+
+- [ ] **Step 4: Run the full test suite**
+
+Run: `pnpm test`
+Expected: PASS — all suites (existing + the new filename, switcher, and library suites).
+
+- [ ] **Step 5: Manual smoke check in the dev server**
+
+Run: `pnpm dev` and open the app, then verify each:
+1. The header shows the current plan name in a dropdown (no more static title).
+2. Open the dropdown → **＋ New plan** adds a plan and switches to it (editor shows the sample again).
+3. Edit the `title` in the source → the dropdown label updates to the new title.
+4. Switch back to the first plan via the dropdown → its source returns.
+5. **⤓ Download .toml** downloads a `macroplan-<slug>.toml` file containing the current source.
+6. The 🗑 button opens a confirm modal naming the active plan; **Cancel** dismisses, **Delete** removes it and switches to the preceding plan.
+7. Delete every plan in turn → the last delete leaves a fresh sample plan (never an empty app).
+8. Reload the page → the library and active plan persist.
+
+Expected: all eight behave as described.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add src/App.vue src/composables/useMacroplan.ts
+git commit -m "feat(ui): wire the plan switcher, delete confirm and .toml download into the app"
+```
+
+---
+
+### Task 5: Documentation
+
+Record the new `Library` term in the ubiquitous language and flip the README now that the library exists.
+
+**Files:**
+- Modify: `CONTEXT.md`
+- Modify: `README.md`
+
+- [ ] **Step 1: Add the `Library` term to `CONTEXT.md`**
+
+In the `## Language` section, immediately after the **Now line** entry (the block ending `_Avoid_: today marker, cursor`) and before `## Symbols`, insert:
+
+```markdown
+
+**Library**:
+The collection of saved **Macroplans** held in the browser's localStorage — the live store. Always holds at least one Macroplan; durability rests on exporting a Macroplan's `.toml` (per ADR-0002), not on the Library itself. Carries no status of its own.
+_Avoid_: workspace, project, file list
+```
+
+- [ ] **Step 2: Add a Library relationship line to `CONTEXT.md`**
+
+In `## Relationships`, after the first bullet (the one starting `A **Macroplan** contains a flat, author-ordered list...`), add:
+
+```markdown
+- The **Library** holds many **Macroplans**, exactly one of which is active (shown in the editor and grid). Each is identified internally by a stable id and labelled by its **title**.
+```
+
+- [ ] **Step 3: Update the README Status paragraph**
+
+Replace:
+
+```markdown
+**Feature-complete** against the [design](DESIGN.md) and covered by tests — TOML authoring with live reload, the full week × feature grid render, derived on-time/late classification, milestones, and PNG export all work client-side.
+
+Not yet built: a **library** of multiple named plans. Today a single source autosaves to localStorage.
+```
+
+with:
+
+```markdown
+**Feature-complete** against the [design](DESIGN.md) and covered by tests — TOML authoring with live reload, a **library** of named plans, the full week × feature grid render, derived on-time/late classification, milestones, and PNG + `.toml` export all work client-side.
+```
+
+- [ ] **Step 4: Update the README "How it works" persistence bullet**
+
+Replace:
+
+```markdown
+- Your source **autosaves to localStorage**; **export a PNG** to share into Slack or a deck.
+```
+
+with:
+
+```markdown
+- Keep a **library** of named plans in localStorage and switch between them; **export** any plan as a `.toml` file, or the rendered view as a **PNG** to share into Slack or a deck.
+```
+
+- [ ] **Step 5: Verify the docs build is unaffected and commit**
+
+Run: `pnpm test`
+Expected: PASS (docs-only change; suites still green).
+
+```bash
+git add CONTEXT.md README.md
+git commit -m "docs: record the Library term and mark the plans library as built"
+```
+
+---
+
+## Self-Review
+
+**1. Spec coverage**
+- Multiple named plans in localStorage → Task 3 (`Library` model).
+- Header dropdown switcher → Task 2 (`PlanSwitcher`) + Task 4 (wiring).
+- New plan from sample → Task 3 (`newPlan`) + Task 4.
+- Delete active plan with confirm → Task 3 (`deletePlan`) + Task 4 (modal).
+- `.toml` download → Task 1 (`sourceFilename`/`downloadSource`) + Task 4.
+- Migration from legacy key + always-≥1 invariant + corrupt fallback + stale-activeId repair → Task 3 (tested).
+- Name = cached last-good title → Task 3 (`titleOf` in the `source` setter, tested).
+- `slugify` extracted, `exportFilename` output unchanged → Task 1 (existing test still passes).
+- Switch resets last-good render → Task 3 (`switchTo`, tested).
+- `Library` glossary term + README flip → Task 5.
+- All spec requirements map to a task. No gaps.
+
+**2. Placeholder scan:** No TBD/TODO-as-deliverable, no "add error handling" hand-waves; every code step shows complete code. The one `TODO(task 4)` comment is a deliberate, scheduled removal (Task 4, Step 1), not an unfinished placeholder.
+
+**3. Type consistency:** `slugify` (Task 1) is consumed by `sourceFilename` (Task 1) and unchanged `exportFilename`. `useMacroplan`'s return shape (Task 3) — `source`, `plan`, `error`, `plans`, `activeId`, `selectPlan`, `newPlan`, `deletePlan` — matches exactly what `App.vue` destructures (Task 4). `PlanSwitcher` props (`plans: {id,name}[]`, `activeId: string`) and emits (`select`, `new`, `download`) match the App template bindings. `StoredPlan`/`Library` are internal to `useMacroplan`. Consistent throughout.