test(ui): poll for the debounced skill auto-save instead of a fixed sleep

Task_toggling_a_skill_auto_saves_selection waited a hard 500 ms for a
debounced save. It passed in isolation and in either half of the suite,
but failed in a full run: this batch added three DB-backed UI test
classes whose real SQLite contexts load the thread pool enough that the
timer callback misses the window. Product code is unchanged.

Same assertion, polled with a 5 s deadline - the pattern the newly added
DetailsIsland/TasksIsland tests already use.

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

@@ -266,7 +266,12 @@ public class AgentConfigEditorViewModelTests
         await vm.LoadForTaskAsync(TaskWith(null, null, "", null));
 
         vm.SessionSkills.Single(s => s.Name == "skill-a").IsSelected = true;
-        await Task.Delay(500);
+
+        // Poll instead of a fixed sleep: the save is debounced, and a full-suite run loads the
+        // thread pool enough that a hard 500 ms wait can expire before the timer callback runs.
+        var deadline = DateTime.UtcNow.AddSeconds(5);
+        while (DateTime.UtcNow < deadline && w.SavedTaskSettings is null)
+            await Task.Delay(25);
 
         Assert.NotNull(w.SavedTaskSettings);
         Assert.Equal(new List<string> { "skill-a" }, w.SavedTaskSettings!.SessionSkills);