feat(ui): add WorktreeStateColorConverter

src/ClaudeDo.Ui/Converters/WorktreeStateColorConverter.cs

@@ -0,0 +1,24 @@
+using System.Globalization;
+using Avalonia.Data.Converters;
+using Avalonia.Media;
+using ClaudeDo.Data.Models;
+
+namespace ClaudeDo.Ui.Converters;
+
+public sealed class WorktreeStateColorConverter : IValueConverter
+{
+    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture) =>
+        value is WorktreeState state
+            ? state switch
+            {
+                WorktreeState.Active    => new SolidColorBrush(Color.Parse("#42A5F5")),
+                WorktreeState.Merged    => new SolidColorBrush(Color.Parse("#66BB6A")),
+                WorktreeState.Discarded => new SolidColorBrush(Color.Parse("#9E9E9E")),
+                WorktreeState.Kept      => new SolidColorBrush(Color.Parse("#FFA726")),
+                _                       => new SolidColorBrush(Colors.Gray),
+            }
+            : new SolidColorBrush(Colors.Gray);
+
+    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => throw new NotSupportedException();
+}