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.

api/openapi.yaml

@@ -312,6 +312,17 @@ paths:
             type: string
         style: form
         explode: true
+      - name: include
+        in: query
+        schema:
+          type: array
+          items:
+            type: string
+            enum:
+            - status
+        style: form
+        explode: true
+        description: include=status joins entity_status and populates GraphView.health
       responses:
         '200':
           description: Graph view
@@ -1696,6 +1707,22 @@ paths:
                 $ref: '#/components/schemas/HealthSummary'
         default:
           $ref: '#/components/responses/Problem'
+  /dashboard/summary:
+    get:
+      tags:
+      - observability
+      operationId: getDashboardSummary
+      summary: One-round-trip overview for the control room home page
+      x-required-scope: viewer
+      responses:
+        '200':
+          description: Dashboard summary
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/DashboardSummary'
+        default:
+          $ref: '#/components/responses/Problem'
   /export:
     get:
       tags:
@@ -1983,6 +2010,16 @@ components:
         truncated:
           type: boolean
           description: True if node cap was hit
+        health:
+          type: object
+          description: entity id -> health, present when include=status was requested
+          additionalProperties:
+            type: string
+            enum:
+            - healthy
+            - degraded
+            - down
+            - unknown
     EntityType:
       type: object
       required:
@@ -3024,6 +3061,69 @@ components:
                 type: string
                 format: date-time
                 nullable: true
+    DashboardSummary:
+      type: object
+      required:
+      - entities_by_type
+      - entities_by_state
+      - health
+      - signals_by_severity
+      - approvals_pending
+      - executions_by_state
+      - event_rate
+      properties:
+        entities_by_type:
+          type: object
+          description: entity counts keyed by type
+          additionalProperties:
+            type: integer
+        entities_by_state:
+          type: object
+          description: entity counts keyed by state
+          additionalProperties:
+            type: integer
+        health:
+          type: object
+          required:
+          - healthy
+          - degraded
+          - down
+          - unknown
+          properties:
+            healthy:
+              type: integer
+            degraded:
+              type: integer
+            down:
+              type: integer
+            unknown:
+              type: integer
+        signals_by_severity:
+          type: object
+          description: open (non-resolved) signal counts keyed by severity
+          additionalProperties:
+            type: integer
+        approvals_pending:
+          type: integer
+        executions_by_state:
+          type: object
+          description: execution counts keyed by state, last 24h
+          additionalProperties:
+            type: integer
+        event_rate:
+          type: array
+          description: event counts bucketed by 5-minute interval, most recent last
+          items:
+            type: object
+            required:
+            - bucket
+            - count
+            properties:
+              bucket:
+                type: string
+                format: date-time
+              count:
+                type: integer
     EnrollRequest:
       type: object
       required: