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.

package.json

@@ -21,6 +21,8 @@
     "test:e2e": "vitest run --config vitest.e2e.config.ts",
     "knip": "knip",
     "publint": "tsx scripts/publint-all.ts",
+    "doc-typecheck": "tsx scripts/doc-typecheck.ts",
+    "verify-event-taxonomy": "tsx scripts/verify-event-taxonomy.ts",
     "hygiene": "yarn knip && yarn publint && yarn constraints",
     "demo:echo": "node --expose-internals --import tsx examples/echo-agent/start.ts",
     "demo:coding": "node --expose-internals --import tsx examples/coding-agent/start.ts",