fix(ui): use BorderOnly chrome; color diff +/- lines

Apply SystemDecorations=BorderOnly + ExtendClientAreaTitleBarHeightHint=-1
to WorktreesOverviewModalView and WorktreeModalView for reliable OS resize
borders. Replace SelectedFileDiff SelectableTextBlock with per-line
ItemsControl using WorktreeDiffLineKind coloring via DiffLineKindToBrushConverter.

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

src/ClaudeDo.Ui/Converters/DiffLineKindToBrushConverter.cs

@@ -0,0 +1,24 @@
+using System.Globalization;
+using Avalonia.Data.Converters;
+using Avalonia.Media;
+using ClaudeDo.Ui.ViewModels.Modals;
+
+namespace ClaudeDo.Ui.Converters;
+
+public sealed class DiffLineKindToBrushConverter : IValueConverter
+{
+    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture) =>
+        value is WorktreeDiffLineKind kind
+            ? kind switch
+            {
+                WorktreeDiffLineKind.Added   => new SolidColorBrush(Color.Parse("#66BB6A")),
+                WorktreeDiffLineKind.Removed => new SolidColorBrush(Color.Parse("#EF5350")),
+                WorktreeDiffLineKind.Hunk    => new SolidColorBrush(Color.Parse("#42A5F5")),
+                WorktreeDiffLineKind.Header  => new SolidColorBrush(Color.Parse("#9E9E9E")),
+                _                            => new SolidColorBrush(Color.Parse("#CFD8DC")),
+            }
+            : new SolidColorBrush(Color.Parse("#CFD8DC"));
+
+    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => throw new NotSupportedException();
+}

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

@@ -5,6 +5,14 @@ using ClaudeDo.Data.Git;
 
 namespace ClaudeDo.Ui.ViewModels.Modals;
 
+public enum WorktreeDiffLineKind { Header, Hunk, Added, Removed, Context }
+
+public sealed partial class WorktreeDiffLineViewModel : ViewModelBase
+{
+    public required string Text { get; init; }
+    public required WorktreeDiffLineKind Kind { get; init; }
+}
+
 public sealed partial class WorktreeNodeViewModel : ViewModelBase
 {
     public required string Name { get; init; }
@@ -19,11 +27,11 @@ public sealed partial class WorktreeModalViewModel : ViewModelBase
     private readonly GitService _git;
 
     public ObservableCollection<WorktreeNodeViewModel> Root { get; } = new();
+    public ObservableCollection<WorktreeDiffLineViewModel> SelectedFileDiffLines { get; } = new();
 
     [ObservableProperty] private string _worktreePath = "";
     [ObservableProperty] private string? _baseCommit;
     [ObservableProperty] private WorktreeNodeViewModel? _selectedNode;
-    [ObservableProperty] private string _selectedFileDiff = "";
 
     // Set by the view (same pattern as DiffModalViewModel.CloseAction)
     public Action? CloseAction { get; set; }
@@ -40,19 +48,33 @@ public sealed partial class WorktreeModalViewModel : ViewModelBase
 
     private async Task LoadFileDiffAsync(WorktreeNodeViewModel? node)
     {
-        if (node is null || node.IsDirectory || string.IsNullOrEmpty(node.RelativePath))
+        SelectedFileDiffLines.Clear();
-        {
-            SelectedFileDiff = "";
-            return;
-        }
 
+        if (node is null || node.IsDirectory || string.IsNullOrEmpty(node.RelativePath))
+            return;
+
+        string diff;
         try
         {
-            SelectedFileDiff = await _git.GetFileDiffAsync(WorktreePath, BaseCommit, node.RelativePath);
+            diff = await _git.GetFileDiffAsync(WorktreePath, BaseCommit, node.RelativePath);
         }
         catch
         {
-            SelectedFileDiff = "";
+            return;
+        }
+
+        foreach (var line in diff.Split('\n'))
+        {
+            var kind = line switch
+            {
+                _ when line.StartsWith("+++") || line.StartsWith("---") => WorktreeDiffLineKind.Header,
+                _ when line.StartsWith("@@")                            => WorktreeDiffLineKind.Hunk,
+                _ when line.StartsWith('+')                             => WorktreeDiffLineKind.Added,
+                _ when line.StartsWith('-')                             => WorktreeDiffLineKind.Removed,
+                _ when line.StartsWith("diff ") || line.StartsWith("index ") || line.StartsWith("\\ ") => WorktreeDiffLineKind.Header,
+                _                                                       => WorktreeDiffLineKind.Context,
+            };
+            SelectedFileDiffLines.Add(new WorktreeDiffLineViewModel { Text = line, Kind = kind });
         }
     }
 

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

@@ -1,18 +1,24 @@
 <Window xmlns="https://github.com/avaloniaui"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:vm="using:ClaudeDo.Ui.ViewModels.Modals"
+        xmlns:converters="using:ClaudeDo.Ui.Converters"
         x:Class="ClaudeDo.Ui.Views.Modals.WorktreeModalView"
         x:DataType="vm:WorktreeModalViewModel"
         Title="Worktree"
         Width="1100" Height="720"
         MinWidth="640" MinHeight="400"
         WindowStartupLocation="CenterOwner"
-        SystemDecorations="None"
+        SystemDecorations="BorderOnly"
         ExtendClientAreaToDecorationsHint="True"
+        ExtendClientAreaTitleBarHeightHint="-1"
         Background="Transparent"
         CanResize="True"
         TransparencyLevelHint="AcrylicBlur">
 
+  <Window.Resources>
+    <converters:DiffLineKindToBrushConverter x:Key="DiffLineKindToBrush"/>
+  </Window.Resources>
+
   <Window.KeyBindings>
     <KeyBinding Gesture="Escape" Command="{Binding CloseCommand}"/>
   </Window.KeyBindings>
@@ -77,11 +83,17 @@
                       HorizontalScrollBarVisibility="Auto"
                       VerticalScrollBarVisibility="Auto"
                       Margin="4,0,8,8">
-          <SelectableTextBlock Text="{Binding SelectedFileDiff}"
+          <ItemsControl ItemsSource="{Binding SelectedFileDiffLines}">
+            <ItemsControl.ItemTemplate>
+              <DataTemplate DataType="vm:WorktreeDiffLineViewModel">
+                <SelectableTextBlock Text="{Binding Text}"
                                      FontFamily="{DynamicResource MonoFont}"
                                      FontSize="11"
-                               Foreground="{DynamicResource TextBrush}"
+                                     Foreground="{Binding Kind, Converter={StaticResource DiffLineKindToBrush}}"
                                      TextWrapping="NoWrap"/>
+              </DataTemplate>
+            </ItemsControl.ItemTemplate>
+          </ItemsControl>
         </ScrollViewer>
 
       </Grid>

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

@@ -9,8 +9,9 @@
         CanResize="True"
         WindowStartupLocation="CenterOwner"
         Background="{DynamicResource SurfaceBrush}"
-        SystemDecorations="None"
+        SystemDecorations="BorderOnly"
-        ExtendClientAreaToDecorationsHint="True">
+        ExtendClientAreaToDecorationsHint="True"
+        ExtendClientAreaTitleBarHeightHint="-1">
 
   <Window.Resources>
     <converters:WorktreeStateColorConverter x:Key="WorktreeStateColor"/>