docs(v0.1): cross-link product spec to companion docs and ADRs

Adds a "Companion docs" header (README, technical, ADR, QFD, roadmap)
and inline pointers from the auth section to ADR-005, the screen
layout to ADR-003, and the acceptance criteria block to qfd §6 — so
each "what must this do" claim has a one-click jump to its rationale
or target.

docs/v0.1-mvp-product.md

@@ -2,6 +2,13 @@
 
 > Scope: the minimum hardware-justifying release. If you take any of this
 > away, the device stops being a typewriter.
+>
+> Companion docs:
+> [README](../README.md) (overview) ·
+> [technical design](v0.1-mvp-technical.md) (how it's built) ·
+> [ADR log](adr.md) (load-bearing decisions) ·
+> [QFD](qfd.md) (requirements ↔ functions ↔ components) ·
+> [roadmap](roadmap.md) (where v0.1 sits in the sequence).
 
 ## One-line summary
 
@@ -69,7 +76,8 @@ That's it. No other stories ship in v0.1.
 If the clone fails (bad PAT, no `notes.md` in the repo, etc.), the screen
 shows the error and offers retry. The repo is expected to already exist on
 GitHub and contain (or be willing to contain) `notes.md` — v0.1 does not
-create remote repos.
+create remote repos. Auth model rationale:
+[ADR-005](adr.md#adr-005-auth--https--github-personal-access-token).
 
 ## Steady-state flow
 
@@ -98,7 +106,7 @@ create remote repos.
 
 GDEY0579T93 — 5.79", **792×272**, 1-bit, partial refresh capable. Wide
 strip aspect (~2.9:1) — biases the UX toward "current line and recent
-context," not a full page.
+context," not a full page. Hardware rationale: [ADR-003](adr.md#adr-003-display--gdey0579t93--despi-c579-breakout).
 
 ```
 ┌─────────────────────────────────────────────────────────────────────────────────────┐
@@ -171,7 +179,10 @@ Explicitly **not** in this release, to keep it shippable:
 
 ## Acceptance criteria
 
-v0.1 ships when **all** of these pass on real hardware:
+v0.1 ships when **all** of these pass on real hardware. Each criterion maps
+to an engineering function with a measured target in
+[qfd.md §6](qfd.md#6-critical-performance-budget); that's the
+place to check before declaring an item done.
 
 - [ ] First-run setup completes in under 5 minutes including typing in a PAT.
 - [ ] After a cold boot with valid config, cursor is ready in ≤ 5 s.