Move UpdatePreviewAsync call to property setter

UpdatePreviewAsync is now called directly in the PreviewSelectedItem setter to ensure immediate updates. Added a debug log for easier troubleshooting.

Author: Jack251970

Flow.Launcher/ViewModel/MainViewModel.cs

@@ -175,9 +175,6 @@ public MainViewModel()
                             QueryResults();
                         }
                         break;
-                    case nameof(PreviewSelectedItem):
-                        _ = UpdatePreviewAsync();
-                        break;
                 }
             };
 
@@ -1195,7 +1192,9 @@ public ResultViewModel PreviewSelectedItem
                 if (_previewSelectedItem != value)
                 {
                     _previewSelectedItem = value;
+                    _ = UpdatePreviewAsync();
                     OnPropertyChanged();
+                    System.Diagnostics.Debug.WriteLine("Update preview");
                 }
             }
         }