layer1: add default watcher config helper

pkg/utils/namespace_manager_test.go

@@ -485,6 +485,30 @@ func TestRunManagedNamespaceWatcher(t *testing.T) {
 	}
 }
 
+func TestNewDefaultManagedNamespaceWatcherConfig(t *testing.T) {
+	resolver := DefaultNSResolver()
+	original := resolver.FissionResourceNS
+	resolver.FissionResourceNS = map[string]string{"tenant-a": "tenant-a"}
+	defer func() {
+		resolver.FissionResourceNS = original
+	}()
+
+	router := &testNamespaceSubscriber{name: "router"}
+	config := NewDefaultManagedNamespaceWatcherConfig("router.NSWatcher", router)
+	if config.Component != "router.NSWatcher" {
+		t.Fatalf("expected component name to be preserved")
+	}
+	if config.RemovalStrategy != NamespaceRemovalStrategyTrackOnly {
+		t.Fatalf("expected default removal strategy track-only")
+	}
+	if !reflect.DeepEqual([]string{"tenant-a"}, config.Namespaces) {
+		t.Fatalf("expected namespaces from resolver snapshot")
+	}
+	if config.Subscriber != router {
+		t.Fatalf("expected subscriber to be preserved")
+	}
+}
+
 func TestPrepareManagedNamespaceWatcherDefaultsToTrackOnly(t *testing.T) {
 	router := &testNamespaceSubscriber{name: "router"}
 	logger := zap.NewNop()