feat(ui): add DescriptionStepsCard detail component

Standalone UserControl combining Description + Steps into one card with
a top-right toggle. Description view shows raw editor or composed
MarkdownView (title + description + open steps). Steps view has an
add-step input and subtask rows with inline editing and check circles.
Adds Icon.Text geometry to IslandStyles for the steps→description toggle.

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

src/ClaudeDo.Ui/Views/Islands/Detail/DescriptionStepsCard.axaml.cs

@@ -0,0 +1,35 @@
+using Avalonia.Controls;
+using Avalonia.Input;
+using Avalonia.Input.Platform;
+using Avalonia.Interactivity;
+using ClaudeDo.Ui.ViewModels.Islands.Detail;
+
+namespace ClaudeDo.Ui.Views.Islands.Detail;
+
+public partial class DescriptionStepsCard : UserControl
+{
+    public DescriptionStepsCard()
+    {
+        InitializeComponent();
+    }
+
+    private async void OnCopyClick(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not DescriptionStepsCardViewModel vm) return;
+        var clipboard = TopLevel.GetTopLevel(this)?.Clipboard;
+        if (clipboard is null) return;
+        await clipboard.SetTextAsync(vm.ComposedPreview);
+    }
+
+    private void OnSubtaskTitleTapped(object? sender, TappedEventArgs e)
+    {
+        if (sender is TextBlock { DataContext: SubtaskRowSampleViewModel row })
+            row.IsEditing = true;
+    }
+
+    private void OnSubtaskEditLostFocus(object? sender, RoutedEventArgs e)
+    {
+        if (sender is TextBox { DataContext: SubtaskRowSampleViewModel row })
+            row.IsEditing = false;
+    }
+}