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.

internal/httpapi/phase3.go

@@ -1835,10 +1835,6 @@ func (s *Server) QueryMetrics(ctx context.Context, req gen.QueryMetricsRequestOb
 	if req.Params.EntityId == nil || *req.Params.EntityId == "" {
 		return nil, fmt.Errorf("%w: entity_id is required", domain.ErrInvalidInput)
 	}
-	if req.Params.Metric == nil || len(*req.Params.Metric) == 0 {
-		return nil, fmt.Errorf("%w: metric is required", domain.ErrInvalidInput)
-	}
-
 	entityID, err := s.resolveEntityID(ctx, *req.Params.EntityId)
 	if err != nil {
 		return nil, err
@@ -1853,8 +1849,33 @@ func (s *Server) QueryMetrics(ctx context.Context, req gen.QueryMetricsRequestOb
 		to = *req.Params.To
 	}
 
+	var metricNames []string
+	if req.Params.Metric != nil && len(*req.Params.Metric) > 0 {
+		metricNames = *req.Params.Metric
+	} else {
+		// metric omitted: report every metric recorded for this entity in range.
+		rows, err := s.pool.Query(ctx, `
+			SELECT DISTINCT metric FROM metric_samples
+			WHERE entity_id = $1 AND ts >= $2 AND ts <= $3
+			ORDER BY metric`, entityID, from, to)
+		if err != nil {
+			return nil, err
+		}
+		for rows.Next() {
+			var name string
+			if err := rows.Scan(&name); err != nil {
+				rows.Close()
+				return nil, err
+			}
+			metricNames = append(metricNames, name)
+		}
+		if err := rows.Err(); err != nil {
+			return nil, err
+		}
+	}
+
 	items := []gen.MetricSeries{}
-	for _, metricName := range *req.Params.Metric {
+	for _, metricName := range metricNames {
 		series := gen.MetricSeries{
 			EntityId: entityID.String(),
 			Metric:   metricName,
@@ -1953,14 +1974,14 @@ func (s *Server) GetTrends(ctx context.Context, req gen.GetTrendsRequestObject)
 			f, _ := slopeNum.Float64Value()
 			t.Slope = float32Ptr(float32(f.Float64))
 			if f.Float64 > 0.01 {
-				t.Direction = gen.Improving
+				t.Direction = gen.TrendDirectionImproving
 			} else if f.Float64 < -0.01 {
-				t.Direction = gen.Degrading
+				t.Direction = gen.TrendDirectionDegrading
 			} else {
-				t.Direction = gen.Stable
+				t.Direction = gen.TrendDirectionStable
 			}
 		} else {
-			t.Direction = gen.Unknown
+			t.Direction = gen.TrendDirectionUnknown
 		}
 		items = append(items, t)
 	}