feat: complete agent monitoring - hook, UI, and backend filter

- Add event_type and framework filters to events query endpoint
- Add /agents SPA route to web-ui server
- Add Agents nav link and route in frontend
- Add agents page CSS (timeline, VM pills, stats panel)
- Build VM status strip, activity timeline, and real-time stats
- Add agentmon hook for OpenClaw (HOOK.md + handler.ts)
- Add docker-compose, Dockerfile, and supporting infra files

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

.gitignore

@@ -1 +1,5 @@
 .worktrees/
+.env
+/ingest-gateway
+/query-api
+/web-ui