feat(ui): add WorkerLogLevelToBrushConverter with tests

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

src/ClaudeDo.Ui/Converters/WorkerLogLevelToBrushConverter.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Globalization;
+using Avalonia;
+using Avalonia.Data.Converters;
+using Avalonia.Media;
+using ClaudeDo.Data.Models;
+
+namespace ClaudeDo.Ui.Converters;
+
+public sealed class WorkerLogLevelToBrushConverter : IValueConverter
+{
+    private static readonly IBrush SuccessBrush = new SolidColorBrush(Color.Parse("#4CAF50"));
+    private static readonly IBrush WarnBrush    = new SolidColorBrush(Color.Parse("#FFA726"));
+    private static readonly IBrush ErrorBrush   = new SolidColorBrush(Color.Parse("#EF5350"));
+    private static readonly IBrush InfoFallback = new SolidColorBrush(Color.Parse("#888888"));
+
+    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        if (value is not WorkerLogLevel level)
+            return AvaloniaProperty.UnsetValue;
+
+        return level switch
+        {
+            WorkerLogLevel.Success => SuccessBrush,
+            WorkerLogLevel.Warn    => WarnBrush,
+            WorkerLogLevel.Error   => ErrorBrush,
+            WorkerLogLevel.Info    => ResolveInfoBrush(),
+            _                      => AvaloniaProperty.UnsetValue,
+        };
+    }
+
+    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture) =>
+        throw new NotSupportedException();
+
+    private static IBrush ResolveInfoBrush()
+    {
+        if (Application.Current is { } app &&
+            app.Resources.TryGetResource("TextDimBrush", app.ActualThemeVariant, out var res) &&
+            res is IBrush brush)
+        {
+            return brush;
+        }
+        return InfoFallback;
+    }
+}