added cache folder sweep check before file actions, preventing errors

lib/widget/downloads/download_tray.dart

@@ -7,6 +7,7 @@ import '../../utils/downloads/download_job.dart';
 import '../../utils/downloads/download_manager.dart';
 import '../../utils/haptics.dart';
 import 'downloads_sheet.dart';
+import 'stale_download_guard.dart';
 
 /// Decides whether a just-finished download should open straight in the viewer.
 ///
@@ -198,9 +199,13 @@ class _DownloadTrayHostState extends State<DownloadTrayHost>
 
   void _openJob(DownloadJob job) {
     final path = job.localPath;
-    _manager.markOpened(job);
     final ctx = AppRoutes.overlayContext;
-    if (path == null || ctx == null) return;
+    if (path == null || ctx == null) {
+      _manager.markOpened(job);
+      return;
+    }
+    if (!ensureDownloadStillExists(ctx, job)) return;
+    _manager.markOpened(job);
     Haptics.success();
     AppRoutes.openFileViewer(ctx, path, remoteFile: job.remoteFile);
   }