docs: final handoff pass

Adds accessibility/README.md, the player-facing setup and keymap reference --
the thing to read before playtesting.

Brings the developer docs in line with what was actually built:

- docs/README.md rewritten as an index with current status and a one-paragraph
  architecture summary.
- docs/scratch.md gains a HANDOFF section: state of play, the commands to run
  after any change, the five traps that each cost real debugging time, what is
  NOT verified and why, deliberate omissions, and how to rebase onto a future
  game version.
- docs/03-implementation-plan.md gains a status banner listing where the
  implementation deliberately diverged from the plan (menu narration pulled
  forward as a blocker, levelCursorPopup not patched, tryInteract insufficient
  as a tracker filter, testbed added, no settings UI built).
- docs/04-open-questions.md gains a resolution banner: Q6 and Q8 remain open.

Also records that the testbed check count varies between runs (23-26) because
some blocks are conditional, so what matters is zero failures rather than the
total.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

accessibility/docs/04-open-questions.md

@@ -1,5 +1,19 @@
 # Open questions
 
+> ## ⚠ Status: mostly answered — see [05-decisions.md](05-decisions.md).
+>
+> **Answered:** Q1 (dev LÖVE; DLLs load by absolute path from
+> `accessibility/lib/`, no elevation needed) · Q2 (tracker hierarchy confirmed) ·
+> Q3 (augment, not relay) · Q4 (speak everything queued; an explicit game action
+> cancels the backlog) · Q5 (wall tones on step, stop-and-replay — confirmed by
+> ear) · Q7 + Q10 (small patches allowed, probe backend kept open for a Steam
+> release) · Q9 (NVDA; `lovec` approved, and a code-driven testbed was built).
+>
+> **Still open:** **Q6** — our hotkeys are currently a separate scheme and are
+> therefore not user-rebindable; integrating them into the game's own rebinding
+> UI is still undecided. **Q8** — no exhaustive keyboard-reachability audit was
+> performed.
+
 Ordered roughly by how much they block work. Q1–Q3 affect the design; the rest are preferences I can pick defaults for if you'd rather not decide up front.
 
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