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/src/lib/components/ui/scroll-area/index.ts

@@ -0,0 +1,10 @@
+import Scrollbar from "./scroll-area-scrollbar.svelte";
+import Root from "./scroll-area.svelte";
+
+export {
+	Root,
+	Scrollbar,
+	//,
+	Root as ScrollArea,
+	Scrollbar as ScrollAreaScrollbar,
+};