style(ui): add strikethrough and dimming for completed tasks

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

src/ClaudeDo.Ui/ViewModels/TaskItemViewModel.cs

@@ -1,3 +1,4 @@
+using Avalonia.Media;
 using ClaudeDo.Data.Models;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
@@ -43,6 +44,16 @@ public partial class TaskItemViewModel : ViewModelBase
     public bool IsRunning => Status == TaskStatus.Running;
     public bool CanToggleDone => Status != TaskStatus.Running && Status != TaskStatus.Failed;
 
+    public TextDecorationCollection? TitleDecorations => IsDone
+        ? TextDecorations.Strikethrough
+        : null;
+
+    public IBrush TitleForeground => IsDone
+        ? new SolidColorBrush(Color.Parse("#5a6578"))
+        : new SolidColorBrush(Color.Parse("#e2e8f0"));
+
+    public double RowOpacity => IsDone ? 0.6 : 1.0;
+
     public void Refresh(TaskEntity entity, IReadOnlyList<TagEntity> tags)
     {
         Entity = entity;
@@ -56,6 +67,9 @@ public partial class TaskItemViewModel : ViewModelBase
         OnPropertyChanged(nameof(IsDone));
         OnPropertyChanged(nameof(IsRunning));
         OnPropertyChanged(nameof(CanToggleDone));
+        OnPropertyChanged(nameof(TitleDecorations));
+        OnPropertyChanged(nameof(TitleForeground));
+        OnPropertyChanged(nameof(RowOpacity));
         ToggleDoneCommand.NotifyCanExecuteChanged();
     }
 

src/ClaudeDo.Ui/Views/TaskListView.axaml

@@ -33,6 +33,7 @@
                 <DataTemplate x:DataType="vm:TaskItemViewModel">
                     <Grid ColumnDefinitions="Auto,*" Margin="4,4"
                           Background="Transparent"
+                          Opacity="{Binding RowOpacity}"
                           DoubleTapped="OnTaskItemDoubleTapped"
                           PointerPressed="OnTaskItemPointerPressed">
                         <Grid.ContextFlyout>
@@ -75,7 +76,8 @@
                         <!-- Task content -->
                         <StackPanel Grid.Column="1" VerticalAlignment="Center">
                             <TextBlock Text="{Binding Title}" FontWeight="Medium"
-                                       Foreground="{StaticResource TextPrimaryBrush}"
+                                       Foreground="{Binding TitleForeground}"
+                                       TextDecorations="{Binding TitleDecorations}"
                                        TextTrimming="CharacterEllipsis"/>
                             <TextBlock FontSize="11"
                                        Foreground="{StaticResource TextDimBrush}"