refactored internal documentation and simplified comments across chat BLoCs, file viewer, and navigation components

lib/notification/notification_controller.dart

@@ -10,12 +10,10 @@ import '../widget/debug/json_viewer.dart';
 import '../widget/info_dialog.dart';
 import 'notification_tasks.dart';
 
-// `vm:entry-point` on the class so AOT tree-shaking doesn't drop it: the
-// FCM background handler runs in a fresh isolate that looks up the class
-// by name from native code.
+// `vm:entry-point` keeps this alive through AOT tree-shaking — the FCM
+// background isolate looks the class up by name from native code.
 @pragma('vm:entry-point')
 class NotificationController {
-  // Notification display is handled by the Firebase SDK using server-generated payloads.
   @pragma('vm:entry-point')
   static Future<void> onBackgroundMessageHandler(RemoteMessage message) async {
     NotificationTasks.updateBadgeCount(message);
@@ -27,10 +25,8 @@ class NotificationController {
   ) async {
     final pushToken = _extractChatToken(message);
     final chatBloc = context.read<ChatBloc>();
-    // hasOpenChat (not currentToken) is the source of truth here:
-    // currentToken sticks around after leaveChat so that didPopNext can
-    // re-claim a stacked chat. Using it would suppress notifications for
-    // the last-opened chat even after the user has navigated away.
+    // hasOpenChat, not currentToken: currentToken sticks around after
+    // leaveChat so didPopNext can re-claim a stacked chat.
     final activeToken = chatBloc.state.data?.currentToken ?? '';
     final chatIsOpen =
         chatBloc.hasOpenChat &&
@@ -41,8 +37,7 @@ class NotificationController {
     NotificationTasks.updateBadgeCount(message);
 
     if (chatIsOpen) {
-      // Long-poll already fetches the message and moves the marker; just
-      // dismiss any tray entry that slipped through foreground rendering.
+      // Long-poll handles the message; just dismiss any stray tray entry.
       unawaited(NotificationTasks.clearNotificationsForChat(pushToken));
       return;
     }