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/Design/IslandStyles.axaml

@@ -85,6 +85,9 @@
     <!-- Icon.ArrowOut — filled arrow for "open external" button -->
     <StreamGeometry x:Key="Icon.ArrowOut">M13 4 H20 V11 H18 V7.4 L11.4 14 L10 12.6 L16.6 6 H13 Z M4 6 H10 V8 H6 V18 H16 V14 H18 V20 H4 Z</StreamGeometry>
 
+    <!-- Icon.Text — three filled horizontal bars (paragraph / description icon) -->
+    <StreamGeometry x:Key="Icon.Text">M4 6 H20 V8 H4 Z M4 11 H20 V13 H4 Z M4 16 H14 V18 H4 Z</StreamGeometry>
+
     <!-- Icon.Warning — filled triangle with exclamation (roadblock badge) -->
     <StreamGeometry x:Key="Icon.Warning">F0 M12 3 L22 20 H2 Z M11 9 H13 V14 H11 Z M11 16 H13 V18 H11 Z</StreamGeometry>
 

src/ClaudeDo.Ui/ViewModels/Islands/Detail/DescriptionStepsCardViewModel.cs

@@ -0,0 +1,133 @@
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.ComponentModel;
+using System.Text;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+
+namespace ClaudeDo.Ui.ViewModels.Islands.Detail;
+
+public partial class SubtaskRowSampleViewModel : ObservableObject
+{
+    [ObservableProperty] string _title = "";
+    [ObservableProperty] bool _done;
+    [ObservableProperty] bool _isEditing;
+
+    [RelayCommand] void ToggleDone() => Done = !Done;
+    [RelayCommand] void BeginEdit() => IsEditing = true;
+    [RelayCommand] void CommitEdit() => IsEditing = false;
+}
+
+public partial class DescriptionStepsCardViewModel : ClaudeDo.Ui.ViewModels.ViewModelBase
+{
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(IsDescriptionView))]
+    bool _isStepsView;
+
+    public bool IsDescriptionView => !IsStepsView;
+
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(ComposedPreview))]
+    string _title = "";
+
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(ComposedPreview))]
+    string _editableDescription = "";
+
+    [ObservableProperty] bool _isEditingDescription;
+    [ObservableProperty] string _newSubtaskTitle = "";
+
+    public ObservableCollection<SubtaskRowSampleViewModel> Subtasks { get; } = new();
+
+    public string ComposedPreview => BuildComposedPreview();
+
+    [RelayCommand] void ToggleCardView() => IsStepsView = !IsStepsView;
+    [RelayCommand] void ToggleEditDescription() => IsEditingDescription = !IsEditingDescription;
+
+    [RelayCommand]
+    void AddSubtask()
+    {
+        if (string.IsNullOrWhiteSpace(NewSubtaskTitle)) return;
+        var row = new SubtaskRowSampleViewModel { Title = NewSubtaskTitle.Trim() };
+        row.PropertyChanged += OnRowPropertyChanged;
+        Subtasks.Add(row);
+        NewSubtaskTitle = "";
+        OnPropertyChanged(nameof(ComposedPreview));
+    }
+
+    [RelayCommand]
+    void ToggleSubtaskDone(SubtaskRowSampleViewModel row)
+    {
+        row.Done = !row.Done;
+    }
+
+    [RelayCommand]
+    void CommitSubtaskEdit(SubtaskRowSampleViewModel row)
+    {
+        row.IsEditing = false;
+    }
+
+    private void OnRowPropertyChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (e.PropertyName is nameof(SubtaskRowSampleViewModel.Done)
+                           or nameof(SubtaskRowSampleViewModel.Title))
+            OnPropertyChanged(nameof(ComposedPreview));
+    }
+
+    private void OnSubtasksChanged(object? sender, NotifyCollectionChangedEventArgs e)
+    {
+        if (e.NewItems is not null)
+            foreach (SubtaskRowSampleViewModel row in e.NewItems)
+                row.PropertyChanged += OnRowPropertyChanged;
+        if (e.OldItems is not null)
+            foreach (SubtaskRowSampleViewModel row in e.OldItems)
+                row.PropertyChanged -= OnRowPropertyChanged;
+        OnPropertyChanged(nameof(ComposedPreview));
+    }
+
+    private string BuildComposedPreview()
+    {
+        var sb = new StringBuilder();
+        sb.AppendLine(Title);
+
+        if (!string.IsNullOrWhiteSpace(EditableDescription))
+        {
+            sb.AppendLine();
+            sb.AppendLine(EditableDescription.TrimEnd());
+        }
+
+        var openSteps = Subtasks.Where(s => !s.Done).ToList();
+        if (openSteps.Count > 0)
+        {
+            sb.AppendLine();
+            sb.AppendLine("## Sub-Tasks");
+            foreach (var step in openSteps)
+                sb.AppendLine($"- [ ] {step.Title}");
+        }
+
+        return sb.ToString().TrimEnd();
+    }
+
+    public DescriptionStepsCardViewModel()
+    {
+        Subtasks.CollectionChanged += OnSubtasksChanged;
+
+        _title = "Refactor diff viewer";
+        _editableDescription =
+            "Split the current monolithic diff renderer into smaller, testable components.\n\n" +
+            "The goal is to improve readability and allow unit testing of each parsing stage independently.";
+
+        var samples = new[]
+        {
+            new SubtaskRowSampleViewModel { Title = "Extract DiffParser into its own class", Done = true },
+            new SubtaskRowSampleViewModel { Title = "Add unit tests for DiffParser",          Done = true },
+            new SubtaskRowSampleViewModel { Title = "Wire new parser into DiffViewerViewModel" },
+            new SubtaskRowSampleViewModel { Title = "Update snapshot tests" },
+        };
+        foreach (var row in samples)
+        {
+            row.PropertyChanged += OnRowPropertyChanged;
+            Subtasks.Add(row);
+        }
+    }
+}

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

@@ -0,0 +1,167 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:vm="using:ClaudeDo.Ui.ViewModels.Islands.Detail"
+             xmlns:ctl="using:ClaudeDo.Ui.Views.Controls"
+             x:Class="ClaudeDo.Ui.Views.Islands.Detail.DescriptionStepsCard"
+             x:DataType="vm:DescriptionStepsCardViewModel">
+
+  <Design.DataContext>
+    <vm:DescriptionStepsCardViewModel/>
+  </Design.DataContext>
+
+  <Border Classes="island">
+    <DockPanel>
+
+      <!-- Header -->
+      <Border DockPanel.Dock="Top" Classes="island-header">
+        <Grid ColumnDefinitions="Auto,*,Auto,Auto,Auto" VerticalAlignment="Center">
+
+          <!-- Col 0: section label -->
+          <Panel Grid.Column="0" VerticalAlignment="Center">
+            <TextBlock Classes="section-label" Text="DETAILS" IsVisible="{Binding IsDescriptionView}"/>
+            <TextBlock Classes="section-label" Text="STEPS"   IsVisible="{Binding IsStepsView}"/>
+          </Panel>
+
+          <!-- Col 1: spacer (auto from *) -->
+
+          <!-- Col 2: Copy button — Description view only -->
+          <Button Grid.Column="2"
+                  Classes="icon-btn"
+                  Margin="0,0,4,0"
+                  ToolTip.Tip="Copy formatted (title + description + open steps)"
+                  IsVisible="{Binding IsDescriptionView}"
+                  Click="OnCopyClick">
+            <PathIcon Data="{StaticResource Icon.Copy}" Width="11" Height="11"/>
+          </Button>
+
+          <!-- Col 3: Preview/Edit toggle — Description view only -->
+          <Button Grid.Column="3"
+                  Classes="btn"
+                  Padding="8,3"
+                  Margin="0,0,4,0"
+                  Command="{Binding ToggleEditDescriptionCommand}"
+                  IsVisible="{Binding IsDescriptionView}">
+            <Panel>
+              <TextBlock Text="Preview" IsVisible="{Binding IsEditingDescription}"/>
+              <TextBlock Text="Edit"    IsVisible="{Binding !IsEditingDescription}"/>
+            </Panel>
+          </Button>
+
+          <!-- Col 4: Card toggle icon -->
+          <Button Grid.Column="4"
+                  Classes="icon-btn"
+                  Command="{Binding ToggleCardViewCommand}"
+                  ToolTip.Tip="Switch Description / Steps">
+            <Panel>
+              <!-- In Description view: show steps/list glyph -->
+              <PathIcon Data="{StaticResource Icon.MoreHorizontal}"
+                        Width="11" Height="11"
+                        IsVisible="{Binding IsDescriptionView}"/>
+              <!-- In Steps view: show text/document glyph -->
+              <PathIcon Data="{StaticResource Icon.Text}"
+                        Width="11" Height="11"
+                        IsVisible="{Binding IsStepsView}"/>
+            </Panel>
+          </Button>
+
+        </Grid>
+      </Border>
+
+      <!-- Body -->
+      <StackPanel Margin="14" Spacing="6">
+
+        <!-- Description view -->
+        <Panel IsVisible="{Binding IsDescriptionView}">
+          <!-- Edit mode: raw TextBox -->
+          <TextBox Text="{Binding EditableDescription, Mode=TwoWay}"
+                   AcceptsReturn="True"
+                   TextWrapping="Wrap"
+                   MinHeight="80"
+                   MaxHeight="320"
+                   Padding="8"
+                   FontFamily="{DynamicResource MonoFont}"
+                   FontSize="{StaticResource FontSizeBody}"
+                   Background="{DynamicResource Surface2Brush}"
+                   BorderBrush="{DynamicResource LineBrush}"
+                   BorderThickness="1"
+                   CornerRadius="8"
+                   IsVisible="{Binding IsEditingDescription}"/>
+          <!-- Preview mode: rendered composed text (title + description + open steps) -->
+          <ctl:MarkdownView Markdown="{Binding ComposedPreview}"
+                            IsVisible="{Binding !IsEditingDescription}"/>
+        </Panel>
+
+        <!-- Steps view -->
+        <StackPanel IsVisible="{Binding IsStepsView}" Spacing="6">
+          <!-- Add-step input -->
+          <TextBox Text="{Binding NewSubtaskTitle, Mode=TwoWay}"
+                   PlaceholderText="Add step…"
+                   Padding="8"
+                   Background="{DynamicResource Surface2Brush}"
+                   BorderBrush="{DynamicResource LineBrush}"
+                   BorderThickness="1"
+                   CornerRadius="8">
+            <TextBox.KeyBindings>
+              <KeyBinding Gesture="Enter" Command="{Binding AddSubtaskCommand}"/>
+            </TextBox.KeyBindings>
+          </TextBox>
+
+          <!-- Subtask rows -->
+          <ItemsControl ItemsSource="{Binding Subtasks}">
+            <ItemsControl.ItemTemplate>
+              <DataTemplate DataType="vm:SubtaskRowSampleViewModel">
+                <Border Classes="subtask-row" Classes.done="{Binding Done}">
+                  <Grid ColumnDefinitions="Auto,*">
+
+                    <!-- Check circle -->
+                    <Button Grid.Column="0"
+                            Classes="flat"
+                            Padding="0"
+                            Margin="0,0,8,0"
+                            VerticalAlignment="Center"
+                            Command="{Binding $parent[ItemsControl].((vm:DescriptionStepsCardViewModel)DataContext).ToggleSubtaskDoneCommand}"
+                            CommandParameter="{Binding}">
+                      <Ellipse Classes="task-check"
+                               Classes.done="{Binding Done}"
+                               Width="16" Height="16"
+                               Cursor="Hand"/>
+                    </Button>
+
+                    <!-- Title / edit -->
+                    <Panel Grid.Column="1" VerticalAlignment="Center">
+                      <TextBlock Classes="subtask-title"
+                                 Text="{Binding Title}"
+                                 IsVisible="{Binding !IsEditing}"
+                                 FontSize="{StaticResource FontSizeBody}"
+                                 Foreground="{DynamicResource TextDimBrush}"
+                                 VerticalAlignment="Center"
+                                 TextWrapping="Wrap"
+                                 Cursor="Ibeam"
+                                 Tapped="OnSubtaskTitleTapped"/>
+                      <TextBox Classes="subtask-edit"
+                               Text="{Binding Title, Mode=TwoWay}"
+                               IsVisible="{Binding IsEditing}"
+                               FontSize="{StaticResource FontSizeBody}"
+                               AcceptsReturn="False"
+                               TextWrapping="Wrap"
+                               LostFocus="OnSubtaskEditLostFocus">
+                        <TextBox.KeyBindings>
+                          <KeyBinding Gesture="Enter"
+                                      Command="{Binding $parent[ItemsControl].((vm:DescriptionStepsCardViewModel)DataContext).CommitSubtaskEditCommand}"
+                                      CommandParameter="{Binding}"/>
+                        </TextBox.KeyBindings>
+                      </TextBox>
+                    </Panel>
+
+                  </Grid>
+                </Border>
+              </DataTemplate>
+            </ItemsControl.ItemTemplate>
+          </ItemsControl>
+        </StackPanel>
+
+      </StackPanel>
+    </DockPanel>
+  </Border>
+
+</UserControl>

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;
+    }
+}