feat(mission-control): custom tiles — open any console program as a tile

Programs are configured in Settings → Custom tiles and stored in ui.config.json.
A tile with a fixed folder starts on click; without one it offers a submenu of
home, the list folders and browse.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ClaudeDo.Ui/Views/Modals/SettingsModalView.axaml.cs

@@ -1,5 +1,8 @@
 using Avalonia.Controls;
+using Avalonia.Interactivity;
+using Avalonia.Platform.Storage;
 using ClaudeDo.Ui.ViewModels.Modals;
+using ClaudeDo.Ui.ViewModels.Modals.Settings;
 
 namespace ClaudeDo.Ui.Views.Modals;
 
@@ -8,7 +11,7 @@ public partial class SettingsModalView : Window
     public SettingsModalView()
     {
         InitializeComponent();
-        
+
     }
 
     protected override void OnDataContextChanged(EventArgs e)
@@ -17,4 +20,11 @@ public partial class SettingsModalView : Window
         if (DataContext is SettingsModalViewModel vm)
             vm.CloseAction = Close;
     }
+
+    private async void OnPickCustomTileFolder(object? sender, RoutedEventArgs e)
+    {
+        if ((sender as Control)?.DataContext is not CustomTileRowViewModel row) return;
+        var folders = await StorageProvider.OpenFolderPickerAsync(new FolderPickerOpenOptions { AllowMultiple = false });
+        if (folders.Count > 0) row.Folder = folders[0].Path.LocalPath;
+    }
 }