Update CLAUDE.md with calendar docs, test patterns, and error conventions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: hubyrod

CLAUDE.md

@@ -60,16 +60,50 @@ GraphQL client with Bearer token auth. `postToSlashwork()` sends formatted markd
 
 ### Webhook verification: `src/webhook.ts`
 
-HMAC-SHA256 signature verification using `node:crypto`. Compares `x-hub-signature-256` header against computed hash.
+HMAC-SHA256 signature verification using `node:crypto.timingSafeEqual`. Compares `x-hub-signature-256` header against computed hash.
+
+### Calendar integration: `src/calendar/`
+
+Google Calendar polling feature that posts upcoming event reminders to Slashwork streams.
+
+- `auth.ts` — JWT creation + Google OAuth token exchange with 5-minute-buffer caching
+- `poller.ts` — Polls calendars at intervals, deduplicates via event keys, hourly cleanup
+- `fetch-events.ts` — Google Calendar API v3 calls
+- `format.ts` — Markdown formatting with video link extraction, HTML stripping
+- `types.ts` — Types matching Google Calendar API response
+
+Calendar config lives in root `config.ts` under `calendar` key. Requires `GOOGLE_SERVICE_ACCOUNT_KEY` env var (full JSON).
+
+## Tests
+
+Test files live next to source: `src/handlers/handlers.test.ts`, `src/webhook.test.ts`, `src/calendar/calendar.test.ts`. Pattern: import `{ test, expect, describe }` from `"bun:test"`.
+
+```sh
+bun test                              # All tests
+bun test --filter "handler"           # Match test file name
+bun test src/calendar/calendar.test.ts  # Run single file
+```
+
+## Error Response Patterns
+
+- Missing/invalid signature → 401
+- Missing headers or unknown event → 200 OK (logged, not forwarded)
+- JSON parse failure → 200 OK (logged)
+- Request body limit: 1MB (`maxRequestBodySize`)
 
 ## Environment Variables
 
 See `.env.example`. Key vars:
 - `GITHUB_WEBHOOK_SECRET` — shared secret for webhook signature verification
 - `SLASHWORK_GRAPHQL_URL` — GraphQL endpoint
 - `SLASHWORK_AUTH_TOKEN_SKIPPER` / `SLASHWORK_AUTH_TOKEN_SKJS` — per-group auth tokens
+- `GOOGLE_SERVICE_ACCOUNT_KEY` — service account JSON for calendar feature (optional)
 - `PORT` — server port (default 3000)
 
+## TypeScript
+
+Strict mode with `noUncheckedIndexedAccess: true`. Target ESNext with bundler module resolution. Type-check: `bunx tsc --noEmit`.
+
 ## Deployment
 
-Clever Cloud via GitHub Actions. Push to `main` → typecheck + tests → auto-deploy.
+Clever Cloud via GitHub Actions (`.github/workflows/deploy.yml`). Push to `main` → typecheck + tests → force-push to Clever Cloud repo → auto-deploy.