fix(ui): notify IsTasksEmptyRepoHintVisible on every list switch

IsTasksEmptyRepoHintVisible reads _currentList?.Kind directly, but Kind
isn't itself observed — the NotifyPropertyChangedFor chain only fires
when IsLetClaudeVisible's value actually changes. Switching from a
Smart list to an empty User list without a WorkingDir changes Kind
while IsLetClaudeVisible (and Has*) stay false in both, so the hint
never notified and stayed stale.

src/ClaudeDo.Ui/ViewModels/Islands/TasksIslandViewModel.cs

@@ -387,6 +387,13 @@ public sealed partial class TasksIslandViewModel : ViewModelBase, IDisposable
         if (_currentList is not null)
             _currentList.PropertyChanged += OnCurrentListPropertyChanged;
 
+        // IsTasksEmptyRepoHintVisible reads _currentList?.Kind directly, but Kind isn't itself an
+        // observed property — the [NotifyPropertyChangedFor] chain only fires when IsLetClaudeVisible's
+        // *value* changes. Switching between two lists that both resolve IsLetClaudeVisible to the
+        // same bool (e.g. a Smart list -> an empty User list without a WorkingDir) changes Kind
+        // without ever notifying, leaving the hint stale. Force it explicitly on every list switch.
+        OnPropertyChanged(nameof(IsTasksEmptyRepoHintVisible));
+
         Items.Clear();
         Rows.Clear();
         HasOverdue    = false;