layer1: stabilize namespace summary contract

pkg/utils/namespace_manager.go

@@ -283,6 +283,9 @@ func (m *inMemoryNamespaceManager) Summary() NamespaceManagerSummary {
 		SourceCounts:    make(map[NamespaceSource]int),
 		Subscribers:     m.SnapshotSubscribers(),
 	}
+	if summary.Subscribers == nil {
+		summary.Subscribers = []string{}
+	}
 	for _, record := range records {
 		summary.PhaseCounts[record.Phase]++
 		summary.SourceCounts[record.Source]++

pkg/utils/namespace_manager_test.go

@@ -582,6 +582,23 @@ func TestLogNamespaceManagerSummary(t *testing.T) {
 
 	LogNamespaceManagerSummary(logger, "namespace summary", summary)
 }
+
+func TestNamespaceManagerSummaryEmptyContract(t *testing.T) {
+	manager := NewNamespaceManager()
+	summary := manager.Summary()
+	if summary.PhaseCounts == nil {
+		t.Fatalf("expected phase counts map to be initialized")
+	}
+	if summary.SourceCounts == nil {
+		t.Fatalf("expected source counts map to be initialized")
+	}
+	if summary.Subscribers == nil {
+		t.Fatalf("expected subscribers slice to be initialized")
+	}
+	if len(summary.Subscribers) != 0 {
+		t.Fatalf("expected no subscribers in empty summary")
+	}
+}
 func TestLogNamespaceManagerSummaryWithNilLogger(t *testing.T) {
 	LogNamespaceManagerSummary(nil, "ignored", NamespaceManagerSummary{TotalNamespaces: 1})
 }