feat(ui): add merge-helper task selection dialog

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

@@ -0,0 +1,81 @@
+<Window xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:vm="using:ClaudeDo.Ui.ViewModels.Modals"
+        xmlns:ctl="using:ClaudeDo.Ui.Views.Controls"
+        xmlns:loc="using:ClaudeDo.Ui.Localization"
+        x:Class="ClaudeDo.Ui.Views.Modals.MergeHelperSelectionModal"
+        x:DataType="vm:MergeHelperSelectionModalViewModel"
+        Title="{loc:Tr modals.mergeHelper.windowTitle}"
+        Width="560" Height="480" MinWidth="420" MinHeight="320"
+        CanResize="True"
+        WindowDecorations="BorderOnly"
+        ExtendClientAreaToDecorationsHint="True"
+        ExtendClientAreaTitleBarHeightHint="-1"
+        WindowStartupLocation="CenterOwner"
+        Background="{DynamicResource SurfaceBrush}">
+  <Window.KeyBindings>
+    <KeyBinding Gesture="Escape" Command="{Binding CancelCommand}"/>
+  </Window.KeyBindings>
+
+  <ctl:ModalShell Title="{loc:Tr modals.mergeHelper.title}" CloseCommand="{Binding CancelCommand}">
+    <ctl:ModalShell.Footer>
+      <StackPanel Orientation="Horizontal" Spacing="8" HorizontalAlignment="Right"
+                  VerticalAlignment="Center">
+        <Button Classes="btn" Content="{loc:Tr modals.mergeHelper.cancel}" Command="{Binding CancelCommand}" MinWidth="90"/>
+        <Button Content="{loc:Tr modals.mergeHelper.confirm}" Command="{Binding ConfirmCommand}"
+                IsEnabled="{Binding CanConfirm}" MinWidth="140" Classes="primary"/>
+      </StackPanel>
+    </ctl:ModalShell.Footer>
+
+    <!-- Body: scope + select-all/none toolbar, headers, checkbox rows -->
+    <DockPanel>
+      <Grid DockPanel.Dock="Top" ColumnDefinitions="*,Auto,Auto" Margin="20,12,20,6">
+        <TextBlock Grid.Column="0" Classes="meta" Text="{Binding ScopeLabel}" VerticalAlignment="Center"/>
+        <Button Grid.Column="1" Classes="btn" Content="{loc:Tr modals.mergeHelper.selectAll}"
+                Command="{Binding SelectAllCommand}" IsEnabled="{Binding HasTasks}"/>
+        <Button Grid.Column="2" Classes="btn" Content="{loc:Tr modals.mergeHelper.selectNone}"
+                Command="{Binding SelectNoneCommand}" IsEnabled="{Binding HasTasks}" Margin="8,0,0,0"/>
+      </Grid>
+
+      <!-- Column headers -->
+      <Grid DockPanel.Dock="Top" ColumnDefinitions="32,*,120,120" Margin="20,0,20,4"
+            IsVisible="{Binding HasTasks}">
+        <TextBlock Grid.Column="1" Classes="eyebrow" Text="{loc:Tr modals.mergeHelper.columnTask}"/>
+        <TextBlock Grid.Column="2" Classes="eyebrow" Text="{loc:Tr modals.mergeHelper.columnStatus}"/>
+        <TextBlock Grid.Column="3" Classes="eyebrow" Text="{loc:Tr modals.mergeHelper.columnList}"
+                   IsVisible="{Binding IsGlobal}"/>
+      </Grid>
+
+      <ScrollViewer Padding="20,2,20,8">
+        <StackPanel>
+          <TextBlock Classes="meta" Margin="0,8"
+                     Text="{loc:Tr modals.mergeHelper.empty}"
+                     IsVisible="{Binding !HasTasks}"/>
+          <ItemsControl ItemsSource="{Binding Tasks}">
+            <ItemsControl.ItemTemplate>
+              <DataTemplate DataType="vm:MergeHelperTaskRowViewModel">
+                <Grid ColumnDefinitions="32,*,120,120" Margin="0,1">
+                  <CheckBox Grid.Column="0" MinWidth="0"
+                            IsChecked="{Binding IsSelected, Mode=TwoWay}"
+                            VerticalAlignment="Center"/>
+                  <TextBlock Classes="body" Grid.Column="1" Text="{Binding Title}"
+                             VerticalAlignment="Center" Margin="4,0,0,0"
+                             TextTrimming="CharacterEllipsis"/>
+                  <Border Grid.Column="2" Classes="chip"
+                          HorizontalAlignment="Left" VerticalAlignment="Center">
+                    <TextBlock Text="{Binding StatusText}"/>
+                  </Border>
+                  <TextBlock Classes="meta" Grid.Column="3" Text="{Binding ListName}"
+                             VerticalAlignment="Center" Margin="8,0,0,0"
+                             TextTrimming="CharacterEllipsis"
+                             IsVisible="{Binding $parent[Window].((vm:MergeHelperSelectionModalViewModel)DataContext).IsGlobal}"/>
+                </Grid>
+              </DataTemplate>
+            </ItemsControl.ItemTemplate>
+          </ItemsControl>
+        </StackPanel>
+      </ScrollViewer>
+    </DockPanel>
+
+  </ctl:ModalShell>
+</Window>

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

@@ -0,0 +1,11 @@
+using Avalonia.Controls;
+
+namespace ClaudeDo.Ui.Views.Modals;
+
+public partial class MergeHelperSelectionModal : Window
+{
+    public MergeHelperSelectionModal()
+    {
+        InitializeComponent();
+    }
+}

src/ClaudeDo.Ui/Views/WindowDialogService.cs

@@ -81,6 +81,15 @@ public sealed class WindowDialogService : IDialogService
         await dlg.ShowDialog(_owner);
     }
 
+    public async Task<System.Collections.Generic.IReadOnlyList<string>?> ShowMergeHelperSelectionAsync(MergeHelperSelectionModalViewModel vm)
+    {
+        var dlg = new MergeHelperSelectionModal { DataContext = vm };
+        vm.CloseAction = () => dlg.Close();
+        dlg.Closed += (_, _) => vm.Result.TrySetResult(null);   // native close counts as cancel
+        await dlg.ShowDialog(_owner);
+        return await vm.Result.Task;
+    }
+
     public async Task ShowWorktreesOverviewAsync(WorktreesOverviewModalViewModel vm)
     {
         var dlg = new WorktreesOverviewModalView { DataContext = vm };