saveTimer method
Persists a workflow timer.
Implementation
@override
Future<void> saveTimer(WorkflowTimer timer) async {
final existingIndex = _timers.indexWhere(
(t) => t.workflowTimerId == timer.workflowTimerId,
);
if (existingIndex >= 0) {
_timers[existingIndex] = timer;
} else {
_timers.add(timer);
}
}