fix(ui): re-evaluate RunNow CanExecute when worker connection changes

Subscribe to WorkerClient.PropertyChanged in TaskListViewModel and call
NotifyCanExecuteChanged on every TaskItemViewModel.RunNowCommand when
IsConnected flips, so the button enables immediately on reconnect without
waiting for the next task DB refresh.

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

src/ClaudeDo.Ui/ViewModels/TaskListViewModel.cs

@@ -44,6 +44,15 @@ public partial class TaskListViewModel : ViewModelBase
 
         worker.TaskUpdatedEvent += OnTaskUpdated;
         worker.TaskFinishedEvent += (_, taskId, _, _) => OnTaskUpdated(taskId);
+        worker.PropertyChanged += (_, e) =>
+        {
+            if (e.PropertyName == nameof(WorkerClient.IsConnected))
+                Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+                {
+                    foreach (var t in Tasks)
+                        t.RunNowCommand.NotifyCanExecuteChanged();
+                });
+        };
     }
 
     public async Task LoadAsync(string? listId)