fix: update loop, ghost queue item, briefing card scroll trap

- Update dialog no longer re-appears on every shell re-mount; check()
  is skipped if status is already available/upToDate/downloading
- Offline queue dequeue now happens before the mounted check, preventing
  ghost items when the widget disposes mid-drain
- Briefing digest card and messages now share a CustomScrollView so
  expanding the card doesn't trap the user without scroll access

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/app.dart

@@ -152,10 +152,14 @@ class _ShellState extends ConsumerState<_Shell> {
   @override
   void initState() {
     super.initState();
-    // Silent update check on first app load.
+    // Silent update check — only if we haven't already checked this session.
+    // Skipping when status is not idle/error prevents the dialog from
+    // re-appearing every time the shell re-mounts (e.g. after visiting settings).
     WidgetsBinding.instance.addPostFrameCallback((_) {
       final repoUrl = ref.read(forgejoRepoUrlProvider);
-      if (repoUrl != null && repoUrl.isNotEmpty) {
+      if (repoUrl == null || repoUrl.isEmpty) return;
+      final status = ref.read(updateProvider).status;
+      if (status == UpdateStatus.idle || status == UpdateStatus.error) {
         ref.read(updateProvider.notifier).check(repoUrl);
       }
     });
@@ -356,8 +360,10 @@ class _QuickCaptureBarState extends ConsumerState<_QuickCaptureBar> {
       if (!mounted) break;
       try {
         final result = await api.capture(text);
-        if (!mounted) break;
+        // Dequeue before the mounted check — SharedPreferences doesn't need
+        // the widget alive, and skipping this would leave a ghost item.
         await ref.read(captureQueueProvider.notifier).dequeue(text);
+        if (!mounted) break;
         switch (result.type) {
           case 'note':
             ref.invalidate(notesProvider);
@@ -368,9 +374,9 @@ class _QuickCaptureBarState extends ConsumerState<_QuickCaptureBar> {
       } on NetworkException {
         break;
       } catch (_) {
-        if (mounted) {
-          await ref.read(captureQueueProvider.notifier).dequeue(text);
-        }
+        // Server error or unexpected failure — drop from queue to prevent
+        // ghost items that can never be cleared.
+        await ref.read(captureQueueProvider.notifier).dequeue(text);
       }
     }
   }