feat(ui): M4 — agent activity, knowledge search, audit, correlation grouping

Add three new pages completing the control-room web UI:
- Agent activity: polls /agent-activity every 5s, filterable by type/agent
- Knowledge search: FTS over /knowledge/search with snippet + entity links
- Audit trail: browseable audit log with actor/action/entity filters

Enhanced live events page with correlation-id clustering (Groups toggle).
Added fetchAgentActivity/searchKnowledge/fetchAudit to the API client.
11 nav items now cover all planned control-room views.

web/tsconfig.json

@@ -8,6 +8,7 @@
     "isolatedModules": true,
     "skipLibCheck": true,
     "paths": {
+      "$lib": ["./src/lib"],
       "$lib/*": ["./src/lib/*"]
     }
   },