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/vite.config.ts

@@ -1,8 +1,9 @@
 import { svelte } from '@sveltejs/vite-plugin-svelte'
+import tailwindcss from '@tailwindcss/vite'
 import { defineConfig } from 'vite'
 
 export default defineConfig({
-  plugins: [svelte()],
+  plugins: [tailwindcss(), svelte()],
   base: '/ui/',
   resolve: {
     alias: { $lib: '/src/lib' }