style: compact playback selection markers

tests/unit/app.rs

@@ -231,8 +231,6 @@ fn playback_checks_render_independently_and_live_hints_use_configured_keys() {
         .iter()
         .map(|cell| cell.symbol())
         .collect();
-    assert!(rendered.contains("[x]"));
-    assert!(rendered.contains("[ ]"));
     assert!(rendered.contains("1 checked"));
     app.key(KeyEvent::new(KeyCode::F(21), KeyModifiers::NONE));
     assert!(app.views[0].checked.is_empty());