feat(018): External Event Adapter

[AlexU-A]

Summary

Complete implementation of kitty-spec 018 — External Event Adapter. Two-tier architecture for platform-native webhooks, cron schedules, and optional external automation forwarding.

• Tier 1 (platform-native): Webhook ingestion (GitHub + generic parsers), HMAC auth, event buffer with DLQ, cron scheduler with timezone support, source CRUD with lifecycle management
• Tier 2 (external automation): Outbound webhook forwarding with circuit breaker (10-failure threshold, 5-min half-open), platform subscriptions with fan-out (20-concurrent limit), trigger callback endpoint
• Admin & observability: Server-rendered admin panel (4 views, XSS-safe), activity log with pagination/filtering/replay, health endpoint with 10 aggregate metrics

Stats

• 13 work packages
• 45 files changed (+14,147 lines)
• ~420 tests across unit, integration, and E2E layers

Architecture

src/event-adapter/
├── parsers/      (GitHub, generic webhook)
├── routes/       (9 route files: admin, automation, events, health, schedules, sources, subscriptions, trigger, webhook)
├── services/     (auth-validator, automation-forwarder, event-buffer, event-translator, payload-mapper, rate-limiter, scheduler, secret-store, trigger-forwarder)
├── workers/      (buffer-drain)
├── schema.ts, types.ts, validation.ts, index.ts

Integration points

• src/index.ts — mounts router at /v1/events
• src/db/client.ts — registers event-adapter schema in Drizzle ORM

Known TODOs

• WP10: POST /trigger bearer token validation is a placeholder (uses raw token as tenant_id)
• WP10/WP11: Pipeline ownership verification requires pipelines table access

Supersedes backlog #9 and #24.

Test plan

• npm run build passes (TypeScript compilation)
• npx vitest run tests/event-adapter/ — all ~420 tests pass
• Review webhook ingestion flow (WP01-05)
• Review cron scheduler (WP06-08)
• Review external automation circuit breaker (WP10)
• Review platform subscriptions fan-out (WP11)
• Review admin panel XSS prevention (WP12)
• Verify E2E integration tests cover cross-service flows (WP13)

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