fix(ui): default-expand diff tree; reliable row-click toggle

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

src/ClaudeDo.Ui/ViewModels/Modals/WorktreeModalViewModel.cs

@@ -20,6 +20,7 @@ public sealed partial class WorktreeNodeViewModel : ViewModelBase
     public bool IsDirectory { get; init; }
     public string RelativePath { get; init; } = "";
     public ObservableCollection<WorktreeNodeViewModel> Children { get; } = new();
+    [ObservableProperty] private bool _isExpanded = true;
 }
 
 public sealed partial class WorktreeModalViewModel : ViewModelBase

src/ClaudeDo.Ui/Views/Modals/WorktreeModalView.axaml

@@ -56,6 +56,11 @@
                   SelectedItem="{Binding SelectedNode, Mode=TwoWay}"
                   Background="Transparent"
                   Margin="8,0,4,8">
+          <TreeView.Styles>
+            <Style Selector="TreeViewItem" x:DataType="vm:WorktreeNodeViewModel">
+              <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
+            </Style>
+          </TreeView.Styles>
           <TreeView.ItemTemplate>
             <TreeDataTemplate DataType="vm:WorktreeNodeViewModel"
                               ItemsSource="{Binding Children}">

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

@@ -62,9 +62,8 @@ public partial class WorktreeModalView : Window
         if (sender is not Control c) return;
         if (c.DataContext is not WorktreeNodeViewModel node) return;
         if (!node.IsDirectory) return;
-        var tvi = c.FindAncestorOfType<TreeViewItem>();
-        if (tvi is null) return;
-        tvi.IsExpanded = !tvi.IsExpanded;
+        node.IsExpanded = !node.IsExpanded;
+        e.Handled = true;
     }
 
     private void OnTitleBarPressed(object? sender, PointerPressedEventArgs e)