=== Case 1: tasks finish comfortably inside the grace period ===
quickPool: shutdown() called, waiting up to 1s for a clean finish
quick-task-1: done (200ms)
quick-task-0: done (200ms)
quickPool: terminated cleanly within the grace period

=== Case 2: a task outlives the grace period, forcing shutdownNow() ===
slowPool: shutdown() called, waiting up to 1s for a clean finish
slow-task: started, will try to sleep 3s
slowPool: grace period expired, escalating to shutdownNow()
slow-task: interrupted during shutdownNow(), stopping early
slowPool: terminated after shutdownNow()
done