docs: add CLAUDE.md so agents start from the accessibility context

New sessions land in what looks like a game repository and start treating the
task as game development, so the accessibility framing had to be re-explained
every time. CLAUDE.md states it up front: everything outside accessibility/ is
the vanilla game and is read-only reference, and a request phrased as a game
bug ("the journal doesn't work") means a screen reader user cannot use it.

Deliberately a pointer rather than a copy, so it cannot drift out of sync with
accessibility/docs/. It sends readers to docs/scratch.md first and carries only
what a fresh agent would otherwise get wrong: that the user is blind so no
verification may depend on seeing anything, the small-footprint rule, that
speech must never throw, the FoV rule, how to run the testbed, and how to read
the startup self-test when something is silent.

CLAUDE.md sits in the game tree, so it would show up in the footprint check
that must stay "main.lua | 1 +". Excluded there and in the three places the
docs quote that command.

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

CLAUDE.md

@@ -0,0 +1,75 @@
+# CLAUDE.md
+
+## What this repository is
+
+This is an extracted copy of the commercial game *Sulphur Memories: Alchemist*
+0.4.2 (LÖVE 11.5, Lua/LuaJIT) — **and the work here is a blind-accessibility mod
+for it, not game development.**
+
+Everything outside `accessibility/` is the vanilla game. Treat it as read-only
+reference material: you read it to find out how the game works, and you patch it
+only in the rare case the docs sanction. All mod code lives in `accessibility/`.
+
+If a request sounds like a game change ("make the journal readable", "the
+inventory doesn't work"), it almost always means **"a screen reader user cannot
+use this"** — the fix belongs in `accessibility/`, not in `states/` or `models/`.
+
+## Read this before doing anything
+
+`accessibility/docs/scratch.md` — a living handoff document. It carries the
+current state of play, confirmed decisions that should not be relitigated, the
+traps that have already cost real debugging time, and what is verified versus
+merely written. **Read it first, and update it before you finish.**
+
+Then `accessibility/docs/README.md` maps the rest: architecture, hooking
+strategy, the phased plan, open questions, decisions.
+
+`accessibility/README.md` is the *user-facing* manual — the key bindings the mod
+adds. Update it when you add or change a key.
+
+## Working agreements
+
+- **The user is blind.** Every verification must be describable in text. Never
+  rely on a screenshot, and never ask them to check something visually. Console
+  output and testbed transcripts are the evidence.
+- **Change as little game code as possible**, so the mod re-applies cleanly to
+  new game versions. Currently the entire game-side footprint is one line in
+  `main.lua`. Check it has not grown:
+  ```
+  git diff --stat vanilla-0.4.2 -- . ':!accessibility' ':!.gitignore' ':!CLAUDE.md'
+  ```
+  It must stay `main.lua | 1 +`. The pristine tree is tagged `vanilla-0.4.2`.
+- **Speech must never throw.** A missing DLL degrades to silence; the game keeps
+  running. Wrappers call through to the original and return its results verbatim.
+- **Never reveal anything outside `FoV` / `rememberedFoV`.** The mod must not
+  become a cheat.
+
+`accessibility/docs/scratch.md` has the full invariant list; these are the ones
+worth knowing before you write a line.
+
+## Verify after any change
+
+```
+lua accessibility/tests/test_history.lua                      # pure Lua, instant
+rm -rf ~/AppData/Roaming/LOVE/Alchemist                       # clean save
+"C:/Program Files/LOVE/lovec.exe" . --a11y-test               # ~4 min
+```
+
+The testbed drives the real game by code and navigates by *reading focus* rather
+than counting keypresses. It has caught essentially every bug in this project, so
+run it — a change that looks obviously correct is exactly the kind that fails.
+
+**What matters is `0 failures`, not the check count**, which varies between runs
+because several blocks are conditional.
+
+Use `lovec.exe` (not `love.exe`) for a console. Every utterance is mirrored there
+as a `[speech]` line, so speech is verifiable from a log rather than only by ear:
+`!` interrupted, `*` immediate, ` ` queued.
+
+## If something mysteriously does not speak
+
+Run the game and read the startup self-test. It reports every patch and every
+descriptor probe. Most menu narration reads the game's file-local variables via
+`debug.getupvalue`, so a renamed local in a future game version shows up there as
+`PROBE BROKEN: no upvalue 'x'` rather than as silence three screens in.
+`ok (unset until opened)` is normal.