feat(ui): pinned Notes row in My Day opens the notes editor

Add ShowNotesRow/OpenNotesCommand to TasksIslandViewModel; wire NotesRequested
event to Details.ShowNotes() in the shell; show a Notes button above the task
list when the My Day smart list is active.

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

src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs

@@ -197,6 +197,7 @@ public sealed partial class IslandsShellViewModel : ViewModelBase
         _repoImportVmFactory = repoImportVmFactory;
         Lists.SelectionChanged += (_, _) => Tasks.LoadForList(Lists.SelectedList);
         Tasks.SelectionChanged += (_, _) => Details.Bind(Tasks.SelectedTask);
+        Tasks.NotesRequested += () => Details.ShowNotes();
         Tasks.TasksChanged     += (_, _) => _ = Lists.RefreshCountsAsync();
         Tasks.OpenListSettingsRequested += (_, _) =>
         {