build: doc-sync gates — typecheck doc code blocks + verify event taxonomy (RFC 006 pts 1-2)

Two tsx CI gates make doc/code drift fail fast:
- doc-typecheck extracts every fenced ts block from README/docs/package READMEs,
  compiles them with tsc --noEmit against a temp project (vendor->lib, harness->src
  paths from tsconfig.typecheck.json), and fails on errors. Deliberate sketches opt
  out with ```ts ignore-check; the opt-out ratio is reported and capped.
- verify-event-taxonomy asserts the docs/architecture.md taxonomy table names
  exactly the events declared in the interface Events blocks. This surfaced three
  events the table had been missing (tools/change, llm/adapter-change,
  system-prompt/change), now added.

Doc snippets made compilable with stub imports/declares (1 genuine sketch ignored).
Wired into CI after typecheck. API reports (RFC 006 pt 3) deferred. Graduates RFC
006 pts 1-2 -> ADR 0014.

packages/tools/README.md

@@ -39,8 +39,12 @@ Tool registry and execution waterfall. Tool plugins register their schemas and e
 First-party plugin authors can use the `defineTool()` helper (exported from this package) for typed tool parameter schemas:
 
 ```ts
+import { readFile } from 'node:fs/promises'
+import type { Context } from 'cordis'
 import { defineTool } from '@deepseek-ai/dsh-tools'
 
+declare const ctx: Context
+
 ctx.tools.register(defineTool({
   name: 'read_file',
   description: 'Read a file from disk.',