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.

tests/ClaudeDo.Ui.Tests/ViewModels/TasksIslandEmptyStateTests.cs

@@ -109,4 +109,31 @@ public class TasksIslandEmptyStateTests : IDisposable
         Assert.False(vm.IsTasksEmptyHintVisible);
         Assert.False(vm.IsTasksEmptyRepoHintVisible);
     }
+
+    // Regression: switching from an empty Smart list (never eligible for the repo hint) to an
+    // empty User list without a WorkingDir changes the correct value of
+    // IsTasksEmptyRepoHintVisible from false to true, but IsLetClaudeVisible stays false in both
+    // cases (Smart lists are never User) and HasOverdue/HasOpen/HasCompleted stay false in both
+    // cases (both lists are empty) — so the [NotifyPropertyChangedFor] chain alone never fires.
+    [Fact]
+    public async Task IsTasksEmptyRepoHintVisible_notifies_on_switch_from_smart_list_to_empty_user_list_without_working_dir()
+    {
+        await using var db = NewContext();
+        db.Lists.Add(new ListEntity { Id = "L4", Name = "Work", CreatedAt = DateTime.UtcNow });
+        await db.SaveChangesAsync();
+
+        var vm = NewVm();
+        vm.LoadForList(new ListNavItemViewModel { Id = "smart:important", Name = "Important", Kind = ListKind.Smart, WorkingDir = null });
+        await vm.LoadTask!;
+        Assert.False(vm.IsTasksEmptyRepoHintVisible);
+
+        var raisedProperties = new List<string?>();
+        vm.PropertyChanged += (_, e) => raisedProperties.Add(e.PropertyName);
+
+        vm.LoadForList(new ListNavItemViewModel { Id = "user:L4", Name = "Work", Kind = ListKind.User, WorkingDir = null });
+        await vm.LoadTask!;
+
+        Assert.Contains(nameof(TasksIslandViewModel.IsTasksEmptyRepoHintVisible), raisedProperties);
+        Assert.True(vm.IsTasksEmptyRepoHintVisible);
+    }
 }