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/pages/Entities.svelte

@@ -0,0 +1,122 @@
+<script lang="ts">
+  import { onMount } from 'svelte'
+  import { fetchEntities, type Entity } from '$lib/api'
+  import { liveEvents, subscribeEvents } from '$lib/stores/events'
+  import * as Table from '$lib/components/ui/table'
+  import { Badge } from '$lib/components/ui/badge'
+  import { Input } from '$lib/components/ui/input'
+  import * as Select from '$lib/components/ui/select'
+  import { Skeleton } from '$lib/components/ui/skeleton'
+
+  let entities = $state<Entity[]>([])
+  let loading = $state(true)
+  let query = $state('')
+  let typeFilter = $state('all')
+
+  async function load() {
+    loading = true
+    entities = await fetchEntities()
+    loading = false
+  }
+
+  onMount(() => {
+    load()
+    const unsubscribe = subscribeEvents()
+    return unsubscribe
+  })
+
+  // Live-patch on entity.* events instead of a full refetch.
+  $effect(() => {
+    const ev = $liveEvents[0]
+    if (!ev || !ev.type.startsWith('entity.')) return
+    load()
+  })
+
+  const types = $derived(Array.from(new Set(entities.map((e) => e.type))).sort())
+
+  const filtered = $derived(
+    entities.filter((e) => {
+      if (typeFilter !== 'all' && e.type !== typeFilter) return false
+      if (query && !e.slug.includes(query) && !e.name.includes(query)) return false
+      return true
+    })
+  )
+
+  function stateVariant(state?: string | null): 'default' | 'secondary' | 'outline' {
+    if (!state) return 'outline'
+    if (state === 'active' || state === 'healthy') return 'default'
+    return 'secondary'
+  }
+</script>
+
+<div class="flex h-full flex-col gap-4 p-6">
+  <div class="flex items-center justify-between">
+    <h1 class="text-lg font-semibold">Entities</h1>
+    <span class="text-xs text-muted-foreground">{filtered.length} of {entities.length}</span>
+  </div>
+
+  <div class="flex gap-2">
+    <Input placeholder="Filter by slug or name…" bind:value={query} class="max-w-xs" />
+    <Select.Root type="single" bind:value={typeFilter}>
+      <Select.Trigger class="w-40">
+        {typeFilter === 'all' ? 'All types' : typeFilter}
+      </Select.Trigger>
+      <Select.Content>
+        <Select.Item value="all">All types</Select.Item>
+        {#each types as type}
+          <Select.Item value={type}>{type}</Select.Item>
+        {/each}
+      </Select.Content>
+    </Select.Root>
+  </div>
+
+  {#if loading}
+    <div class="flex flex-col gap-2">
+      {#each Array(8) as _}
+        <Skeleton class="h-8 w-full" />
+      {/each}
+    </div>
+  {:else}
+    <div class="flex-1 overflow-auto rounded-md border">
+      <Table.Root>
+        <Table.Header>
+          <Table.Row>
+            <Table.Head>Slug</Table.Head>
+            <Table.Head>Type</Table.Head>
+            <Table.Head>Name</Table.Head>
+            <Table.Head>State</Table.Head>
+            <Table.Head>Updated</Table.Head>
+          </Table.Row>
+        </Table.Header>
+        <Table.Body>
+          {#each filtered as entity (entity.id)}
+            <Table.Row
+              class="cursor-pointer"
+              onclick={() => (location.hash = '#/entity/' + encodeURIComponent(entity.slug))}
+            >
+              <Table.Cell class="font-mono text-xs">{entity.slug}</Table.Cell>
+              <Table.Cell><Badge variant="outline">{entity.type}</Badge></Table.Cell>
+              <Table.Cell>{entity.name}</Table.Cell>
+              <Table.Cell>
+                {#if entity.state}
+                  <Badge variant={stateVariant(entity.state)}>{entity.state}</Badge>
+                {:else}
+                  <span class="text-muted-foreground">—</span>
+                {/if}
+              </Table.Cell>
+              <Table.Cell class="text-xs text-muted-foreground"
+                >{new Date(entity.updated_at).toLocaleString()}</Table.Cell
+              >
+            </Table.Row>
+          {:else}
+            <Table.Row>
+              <Table.Cell colspan={5} class="text-center text-muted-foreground"
+                >No entities match this filter.</Table.Cell
+              >
+            </Table.Row>
+          {/each}
+        </Table.Body>
+      </Table.Root>
+    </div>
+  {/if}
+</div>