fix(feed): improve feed decorator status updates and popup menu

- Enhance logic for updating UserFeedDecoratorStatus in AppBloc
- Fix type of PopupMenuButton in ContentCollectionView

Author: fulleni

lib/app/bloc/app_bloc.dart

@@ -361,8 +361,12 @@ class AppBloc extends Bloc<AppEvent, AppState> {
           const UserFeedDecoratorStatus(isCompleted: false);
 
       final updatedDecoratorStatus = currentStatus.copyWith(
+        // Always update the last shown timestamp.
         lastShownAt: now,
-        isCompleted: event.isCompleted || currentStatus.isCompleted,
+        // If the event marks it as completed, it should be completed.
+        // Otherwise, respect the existing completion status. This prevents
+        // a non-completed event from overriding a completed one.
+        isCompleted: event.isCompleted ? true : currentStatus.isCompleted,
       );
 
       final newFeedDecoratorStatus =

lib/feed_decorators/widgets/content_collection_decorator_widget.dart

@@ -113,13 +113,13 @@ class _ContentCollectionViewState extends State<_ContentCollectionView> {
                   ),
                 ),
                 if (widget.onDismiss != null)
-                  PopupMenuButton<void>(
+                  PopupMenuButton<String>(
                     icon: const Icon(Icons.more_vert),
                     tooltip: l10n.decoratorDismissAction,
                     onSelected: (_) => widget.onDismiss!(),
                     itemBuilder: (BuildContext context) => [
-                      PopupMenuItem<void>(
-                        value: null,
+                      PopupMenuItem<String>(
+                        value: 'dismiss',
                         child: Text(l10n.decoratorDismissAction),
                       ),
                     ],