feat(ui): tasks island with rows, chips, add-task, selection

TaskRowView with status chip (EqStatus converter + parameter),
StrikeIfTrue, NotNullToBool converters. TasksIslandView with header,
add-task TextBox (Enter=AddCommand), ItemsControl + flat Button for
selection. Converters registered in App.axaml.

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

src/ClaudeDo.Ui/Converters/EqStatusConverter.cs

@@ -0,0 +1,26 @@
+using System.Globalization;
+using Avalonia.Data.Converters;
+using ClaudeDo.Data.Models;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Ui.Converters;
+
+/// <summary>
+/// Returns true when the bound TaskStatus equals the ConverterParameter string.
+/// Usage: Classes.running="{Binding Status, Converter={StaticResource EqStatus}, ConverterParameter=Running}"
+/// </summary>
+public class EqStatusConverter : IValueConverter
+{
+    public static EqStatusConverter Instance { get; } = new();
+
+    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        if (value is TaskStatus status && parameter is string name &&
+            Enum.TryParse<TaskStatus>(name, ignoreCase: true, out var target))
+            return status == target;
+        return false;
+    }
+
+    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => throw new NotSupportedException();
+}