feat(ui): worker-menu Shutdown ends worker + app after confirm

Adds a Shutdown entry after the Worker menu's Restart/Update Claude CLI
items. Confirms via IDialogService.ConfirmAsync, then kills this
installation's ClaudeDo.Worker process(es) (shared kill loop, extracted
from RestartWorkerService) and force-closes the window through the same
_forceClose path MainWindow already uses for the Mission-Control close
confirm, so no second confirmation dialog shows.

src/ClaudeDo.Ui/Views/MainWindow.axaml.cs

@@ -80,6 +80,11 @@ public partial class MainWindow : Window
                     WindowState = WindowState.Normal;
                 Activate();
             };
+            vm.CloseWindow = () =>
+            {
+                _forceClose = true;
+                Close();
+            };
             if (vm.Tasks is not null)
                 vm.Tasks.IsWindowVisible = WindowState != WindowState.Minimized;
         }