feat(ui): keyboard shortcuts (/ Ctrl+N Space Esc)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -6,7 +6,22 @@ namespace ClaudeDo.Ui.Views;
 
 public partial class MainWindow : Window
 {
-    public MainWindow() { InitializeComponent(); }
+    public MainWindow()
+    {
+        InitializeComponent();
+        KeyDown += OnWindowKeyDown;
+    }
+
+    private void OnWindowKeyDown(object? sender, KeyEventArgs e)
+    {
+        if (e.Key == Key.Space
+            && FocusManager?.GetFocusedElement() is not TextBox
+            && DataContext is IslandsShellViewModel vm)
+        {
+            e.Handled = true;
+            _ = vm.ToggleSelectedDoneAsync();
+        }
+    }
 
     private void OnTitleBarPressed(object? sender, PointerPressedEventArgs e)
     {