rename(547): what people read says Grimoire

Step 1 of the Scribe -> Grimoire rename: every capitalised "Scribe" in prose
becomes "Grimoire" ("Fabled Scribe" -> "Fabled Grimoire") across the UI,
the PWA manifest and page title, the MCP instructions and tool docstrings,
hook and skill text, docs and README, with the tests that assert on that
prose moving with it. Old migrations keep their wording.

Identifiers are untouched here: the package, plugin name, MCP server key,
hook file names, env vars, the .scribe marker and FabledScribe repo/image
names move in steps 2 and 3, along with prose that quotes them.

The sweep matched "Scribe" only as a whole word, so describe/subscribe and
friends are untouched. The longer name took the MCP instructions one
character over their 1,600 budget; two phrases are shortened to fit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/api-reference.md

@@ -291,7 +291,7 @@ These serve the plugin's hooks.
 |--------|------|-------------|
 | POST | `/api/webhooks/forge` | Push events from a git forge, verified with `FORGE_WEBHOOK_SECRET` **(public)** |
 
-## Scribe MCP
+## Grimoire MCP
 
 Claude clients connect to the built-in MCP server at `POST /mcp` (streamable HTTP,
 Bearer auth with an `fmcp_` key), served by `src/scribe/mcp/`. It is not a REST