fix: harden download errors and re-enrich sidecars

lib/widgets/app_announcement_dialog.dart

@@ -12,60 +12,107 @@ class AppAnnouncementDialog extends StatelessWidget {
     required this.onDismiss,
   });
 
+  void _close(BuildContext context) {
+    onDismiss();
+    Navigator.pop(context);
+  }
+
   Future<void> _openCta(BuildContext context) async {
     final ctaUrl = announcement.ctaUrl;
-    if (ctaUrl == null || ctaUrl.isEmpty) return;
+    if (ctaUrl == null || ctaUrl.isEmpty) {
+      _showCtaOpenFailed(context);
+      return;
+    }
 
     final uri = Uri.tryParse(ctaUrl);
-    if (uri == null) return;
+    if (uri == null) {
+      _showCtaOpenFailed(context);
+      return;
+    }
+
+    bool launched;
+    try {
+      launched = await launchUrl(uri, mode: LaunchMode.externalApplication);
+    } catch (_) {
+      launched = false;
+    }
+    if (!launched) {
+      _showCtaOpenFailed(context);
+      return;
+    }
 
-    await launchUrl(uri, mode: LaunchMode.externalApplication);
     onDismiss();
     if (context.mounted) {
       Navigator.pop(context);
     }
   }
 
+  void _showCtaOpenFailed(BuildContext context) {
+    if (!context.mounted) return;
+    ScaffoldMessenger.maybeOf(context)?.showSnackBar(
+      const SnackBar(content: Text('Unable to open link. Please try again.')),
+    );
+  }
+
   @override
   Widget build(BuildContext context) {
     final colorScheme = Theme.of(context).colorScheme;
     final isUrgent = announcement.priority.toLowerCase() == 'high';
 
-    return AlertDialog(
-      icon: Icon(
-        isUrgent ? Icons.priority_high_rounded : Icons.campaign_rounded,
-        color: isUrgent ? colorScheme.error : colorScheme.primary,
-      ),
-      title: Text(announcement.title),
-      content: ConstrainedBox(
-        constraints: const BoxConstraints(maxHeight: 260),
-        child: SingleChildScrollView(
-          child: Text(
-            announcement.message,
-            style: Theme.of(
-              context,
-            ).textTheme.bodyMedium?.copyWith(height: 1.45),
+    // The notice can only be closed through an explicit affordance: never by
+    // tapping the scrim or the system back button (handled by the barrier and
+    // PopScope below). Always keep at least one way out (the X). A
+    // non-dismissible announcement may omit the X only when it carries a CTA,
+    // so the user can never get permanently trapped.
+    final showCloseButton = announcement.dismissible || !announcement.hasCta;
+
+    final actions = <Widget>[
+      if (announcement.hasCta)
+        FilledButton(
+          onPressed: () => _openCta(context),
+          child: Text(announcement.ctaLabel!),
+        ),
+    ];
+
+    return PopScope(
+      canPop: false,
+      child: AlertDialog(
+        title: Row(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Icon(
+              isUrgent ? Icons.priority_high_rounded : Icons.campaign_rounded,
+              color: isUrgent ? colorScheme.error : colorScheme.primary,
+            ),
+            const SizedBox(width: 12),
+            Expanded(
+              child: Padding(
+                padding: const EdgeInsets.only(top: 2),
+                child: Text(announcement.title),
+              ),
+            ),
+            if (showCloseButton)
+              IconButton(
+                icon: const Icon(Icons.close_rounded),
+                tooltip: MaterialLocalizations.of(context).closeButtonTooltip,
+                visualDensity: VisualDensity.compact,
+                onPressed: () => _close(context),
+              ),
+          ],
+        ),
+        content: ConstrainedBox(
+          constraints: const BoxConstraints(maxHeight: 260),
+          child: SingleChildScrollView(
+            child: Text(
+              announcement.message,
+              style: Theme.of(
+                context,
+              ).textTheme.bodyMedium?.copyWith(height: 1.45),
+            ),
           ),
         ),
+        actions: actions.isEmpty ? null : actions,
       ),
-      actions: [
-        TextButton(
-          onPressed: () {
-            onDismiss();
-            Navigator.pop(context);
-          },
-          child: Text(
-            announcement.dismissible
-                ? MaterialLocalizations.of(context).closeButtonLabel
-                : 'OK',
-          ),
-        ),
-        if (announcement.hasCta)
-          FilledButton(
-            onPressed: () => _openCta(context),
-            child: Text(announcement.ctaLabel!),
-          ),
-      ],
     );
   }
 }
@@ -75,10 +122,14 @@ Future<void> showAppAnnouncementDialog(
   required RemoteAnnouncement announcement,
   required VoidCallback onDismiss,
 }) {
+  // barrierDismissible is false so a stray tap outside the dialog can no longer
+  // close (and silently mark-as-seen) the notice. Dismissal — and the
+  // mark-as-seen side effect in onDismiss — only happens via the explicit close
+  // button or the CTA, both of which call onDismiss themselves.
   return showDialog<void>(
     context: context,
-    barrierDismissible: announcement.dismissible,
+    barrierDismissible: false,
     builder: (context) =>
         AppAnnouncementDialog(announcement: announcement, onDismiss: onDismiss),
-  ).whenComplete(onDismiss);
+  );
 }