feat(telemetry): anonymous usage telemetry — documented schema, opt-out, public ingest worker (#834)

Adds anonymous usage statistics (commands/tools used, languages indexed,
connecting agents) with a strict, auditable allowlist. Never code, paths,
file/symbol names, queries, or IPs.

- src/telemetry/: zero-dep client — consent resolution (DO_NOT_TRACK >
  CODEGRAPH_TELEMETRY > stored choice > default-on), random machine UUID,
  in-memory counters → capped JSONL buffer → completed-day rollups; sync
  exit-append (survives process.exit) + opportunistic bounded sends; the
  first-run notice gates the first SEND, never local buffering, so the
  installer's consent toggle always precedes it. Off is off: no recording,
  no socket, buffered data deleted.
- codegraph telemetry status|on|off; per-command counting via preAction hook.
- MCP: tool counting after the reply is on the wire (session + proxy
  in-process fallback), agent attribution from initialize clientInfo,
  unref'd daemon flush interval. Zero hot-path cost, zero stdout.
- Installer: visible default-on consent toggle (asked once, never re-asked),
  install/index/uninstall lifecycle events.
- telemetry-worker/: public Cloudflare Worker behind telemetry.getcodegraph.com
  — allowlist validation, IP stripping, per-machine rate limit, forwards to
  PostHog as anonymous events. Ships nowhere with the npm package.
- TELEMETRY.md (field-by-field contract) + README section + design doc.
- 20 unit tests; suite-wide CODEGRAPH_TELEMETRY=0 guard so tests never
  pollute real telemetry. Full suite: 1448 passing.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

telemetry-worker/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "codegraph-telemetry-worker",
+  "private": true,
+  "description": "First-party ingest endpoint for codegraph's anonymous usage telemetry (telemetry.getcodegraph.com)",
+  "scripts": {
+    "dev": "wrangler dev",
+    "deploy": "wrangler deploy",
+    "types": "wrangler types",
+    "check": "wrangler types && tsc --noEmit && wrangler deploy --dry-run"
+  },
+  "devDependencies": {
+    "typescript": "^5.0.0",
+    "wrangler": "^4.36.0"
+  }
+}