fix: sidebar Pilot test race — add await pilot.pause() before widget query

test_sidebar_shows_status_bar was querying #status before Textual
finished composing the widget tree. Adding pilot.pause() matches the
pattern used by the adjacent test_sidebar_shows_timer_widget.

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

Author: taylaand

packages/studyctl/tests/test_sidebar_pilot.py

@@ -96,6 +96,7 @@ async def test_sidebar_shows_status_bar(self, state_dir):
         )
 
         async with SidebarApp().run_test(size=(40, 20)) as pilot:
+            await pilot.pause()  # let mount + compose complete
             status = pilot.app.query_one("#status")
             assert "pause" in str(status.render()).lower() or "p:" in str(status.render())