fix: selection race condition (#1194)

* fix: guard debounced desktop selection update

Avoid dereferencing a cleared selection from the delayed
macOS metrics callback and add a regression test that
covers the stale-timer path.

* chore: clean up analyzer warnings

Remove redundant default arguments in tests and apply the
missing trailing comma required by the current lint rules.

test/new/service/shortcuts/command_shortcut_events/undo_redo_command_test.dart

@@ -203,7 +203,7 @@ void main() async {
 
       // Place cursor at [0] offset 0
       await editor.updateSelection(
-        Selection.collapsed(Position(path: [0], offset: 0)),
+        Selection.collapsed(Position(path: [0])),
       );
 
       // Type 4 characters with pumpAndSettle between each