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/Views/Islands/TaskRowView.axaml.cs

@@ -0,0 +1,8 @@
+using Avalonia.Controls;
+
+namespace ClaudeDo.Ui.Views.Islands;
+
+public partial class TaskRowView : UserControl
+{
+    public TaskRowView() { InitializeComponent(); }
+}