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/dashboard.go

@@ -0,0 +1,160 @@
+package httpapi
+
+import (
+	"context"
+	"time"
+
+	"github.com/dtoro/oikos/internal/httpapi/gen"
+)
+
+// GetDashboardSummary returns one round-trip overview for the control room
+// home page: entity counts, health rollup, open signals, pending approvals,
+// executions in the last 24h, and an event-rate sparkline.
+func (s *Server) GetDashboardSummary(ctx context.Context, req gen.GetDashboardSummaryRequestObject) (gen.GetDashboardSummaryResponseObject, error) {
+	resp := gen.DashboardSummary{
+		EntitiesByType:    map[string]int{},
+		EntitiesByState:   map[string]int{},
+		SignalsBySeverity: map[string]int{},
+		ExecutionsByState: map[string]int{},
+	}
+
+	rows, err := s.pool.Query(ctx, `SELECT type, count(*) FROM entities GROUP BY type`)
+	if err != nil {
+		return nil, err
+	}
+	for rows.Next() {
+		var typ string
+		var n int
+		if err := rows.Scan(&typ, &n); err != nil {
+			rows.Close()
+			return nil, err
+		}
+		resp.EntitiesByType[typ] = n
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+
+	rows, err = s.pool.Query(ctx, `SELECT coalesce(state, 'unknown'), count(*) FROM entities GROUP BY state`)
+	if err != nil {
+		return nil, err
+	}
+	for rows.Next() {
+		var state string
+		var n int
+		if err := rows.Scan(&state, &n); err != nil {
+			rows.Close()
+			return nil, err
+		}
+		resp.EntitiesByState[state] = n
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+
+	rows, err = s.pool.Query(ctx, `SELECT health, count(*) FROM entity_status GROUP BY health`)
+	if err != nil {
+		return nil, err
+	}
+	for rows.Next() {
+		var health string
+		var n int
+		if err := rows.Scan(&health, &n); err != nil {
+			rows.Close()
+			return nil, err
+		}
+		switch health {
+		case "healthy":
+			resp.Health.Healthy = n
+		case "degraded":
+			resp.Health.Degraded = n
+		case "down":
+			resp.Health.Down = n
+		default:
+			resp.Health.Unknown = n
+		}
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+
+	rows, err = s.pool.Query(ctx, `
+		SELECT severity, count(*) FROM signals
+		WHERE state NOT IN ('resolved', 'failed')
+		GROUP BY severity`)
+	if err != nil {
+		return nil, err
+	}
+	for rows.Next() {
+		var severity string
+		var n int
+		if err := rows.Scan(&severity, &n); err != nil {
+			rows.Close()
+			return nil, err
+		}
+		resp.SignalsBySeverity[severity] = n
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+
+	if err := s.pool.QueryRow(ctx,
+		`SELECT count(*) FROM approvals WHERE status = 'pending'`,
+	).Scan(&resp.ApprovalsPending); err != nil {
+		return nil, err
+	}
+
+	rows, err = s.pool.Query(ctx, `
+		SELECT status, count(*) FROM executions
+		WHERE created_at > now() - interval '24 hours'
+		GROUP BY status`)
+	if err != nil {
+		return nil, err
+	}
+	for rows.Next() {
+		var status string
+		var n int
+		if err := rows.Scan(&status, &n); err != nil {
+			rows.Close()
+			return nil, err
+		}
+		resp.ExecutionsByState[status] = n
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+
+	rows, err = s.pool.Query(ctx, `
+		SELECT date_trunc('hour', ts) + (extract(minute FROM ts)::int / 5) * interval '5 minutes' AS bucket,
+		       count(*)
+		FROM events
+		WHERE ts > now() - interval '6 hours'
+		GROUP BY bucket
+		ORDER BY bucket`)
+	if err != nil {
+		return nil, err
+	}
+	for rows.Next() {
+		var bucket time.Time
+		var n int
+		if err := rows.Scan(&bucket, &n); err != nil {
+			rows.Close()
+			return nil, err
+		}
+		resp.EventRate = append(resp.EventRate, struct {
+			Bucket time.Time `json:"bucket"`
+			Count  int       `json:"count"`
+		}{Bucket: bucket, Count: n})
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+
+	return gen.GetDashboardSummary200JSONResponse(resp), nil
+}