feat(completion): suggest dates in date value positions

The TOML editor offered nothing when typing a date, leaving the
yyyy-mm-dd format undiscoverable until a parse error. Suggest today
(a full, easy-to-edit date) and the current-year prefix on empty
date values and fresh reestimates elements, backing off once a date
is being typed.

src/components/completion.test.ts

@@ -81,6 +81,50 @@ describe("completion context", () => {
   })
 })
 
+describe("date completion", () => {
+  const TODAY = "2026-06-19"
+  const datesAt = (marked: string) => {
+    const [source, caret] = atCaret(marked)
+    return getCompletions(source, caret, TODAY)
+  }
+
+  it("suggests today then the current-year prefix for an empty date value", () => {
+    const ctx = datesAt("[[feature]]\nstart = |")!
+    expect(ctx.items.map((i) => i.insert)).toEqual(["2026-06-19", "2026-"])
+    expect(ctx.items.map((i) => i.detail)).toEqual(["today", "this year"])
+  })
+
+  it("offers the same for plan dates and milestone weeks", () => {
+    expect(datesAt("end = |")!.items.map((i) => i.insert)).toEqual(["2026-06-19", "2026-"])
+    expect(datesAt("[[milestone]]\nweek = |")!.items.map((i) => i.insert)).toEqual([
+      "2026-06-19",
+      "2026-",
+    ])
+  })
+
+  it("inserts at the caret, replacing nothing", () => {
+    const [source, caret] = atCaret("[[feature]]\ndelivered = |")
+    const ctx = getCompletions(source, caret, TODAY)!
+    expect([ctx.from, ctx.to]).toEqual([caret, caret])
+  })
+
+  it("offers a date for a fresh element in a reestimates array", () => {
+    expect(datesAt("[[feature]]\nreestimates = [|")!.items.map((i) => i.insert)).toEqual([
+      "2026-06-19",
+      "2026-",
+    ])
+    expect(
+      datesAt("[[feature]]\nreestimates = [2026-01-01, |")!.items.map((i) => i.insert),
+    ).toEqual(["2026-06-19", "2026-"])
+  })
+
+  it("stays out of the way once a date is being typed", () => {
+    expect(datesAt("[[feature]]\nstart = 2|")).toBeNull()
+    expect(datesAt("[[feature]]\nstart = 2026-|")).toBeNull()
+    expect(datesAt("[[feature]]\nreestimates = [2026-0|")).toBeNull()
+  })
+})
+
 describe("completion replace range", () => {
   it("replaces the typed prefix, not the whole line", () => {
     const source = "[[feature]]\nst"

src/components/completion.ts

@@ -53,8 +53,13 @@ const HEADERS: Completion[] = [
 
 const STATUSES = ["on-track", "at-risk", "off-track"] // keep in sync with parse.ts
 
-/** What to suggest at `caret` in `source`, or null when nothing applies. */
-export function getCompletions(source: string, caret: number): CompletionContext | null {
+/** What to suggest at `caret` in `source`, or null when nothing applies.
+ *  `today` (yyyy-mm-dd) seeds the date suggestions; injectable for tests. */
+export function getCompletions(
+  source: string,
+  caret: number,
+  today: string = todayYmd(),
+): CompletionContext | null {
   const lineStart = source.lastIndexOf("\n", caret - 1) + 1
   const linePrefix = source.slice(lineStart, caret)
 
@@ -68,6 +73,19 @@ export function getCompletions(source: string, caret: number): CompletionContext
     return result(lineStart + status[1].length, caret, items)
   }
 
+  // ── value: a date field — start = <here>, week = <here>, … ────────────────
+  // Only on an empty value, so it never fights a date already being typed
+  // (the chained refresh after picking the key surfaces these immediately).
+  if (/^\s*(?:start|end|original|delivered|week)\s*=\s*$/.test(linePrefix)) {
+    return result(caret, caret, dateItems(today))
+  }
+
+  // ── value: reestimates = [ … <here> ] — a date for a fresh array element ──
+  const inReestimates = /reestimates\s*=\s*\[[^\]]*$/.test(linePrefix)
+  if (inReestimates && /[[,]\s*$/.test(linePrefix)) {
+    return result(caret, caret, dateItems(today))
+  }
+
   const block = currentBlock(source, lineStart)
 
   // ── value: requires = [ "<here>" … ]  (milestones only) ───────────────────
@@ -101,6 +119,20 @@ function result(from: number, to: number, items: Completion[]): CompletionContex
   return items.length ? { from, to, items } : null
 }
 
+/** Today as yyyy-mm-dd (UTC, matching `toYmd`). Injectable keeps tests stable. */
+function todayYmd(): string {
+  return new Date().toISOString().slice(0, 10)
+}
+
+/** Date suggestions: the full date (easy to tweak the day/month in place) and
+ *  the current-year prefix (accept it, then type the month-day). */
+function dateItems(today: string): Completion[] {
+  return [
+    { label: today, insert: today, detail: "today" },
+    { label: today.slice(0, 5), insert: today.slice(0, 5), detail: "this year" },
+  ]
+}
+
 function filter(items: Completion[], word: string): Completion[] {
   if (!word) return items
   const w = word.toLowerCase()