Function flush

src/pkg/utils/async_queue.test.ts:12–16

()

const nextTick = () => Promise.resolve();
/** 强制执行所有已入队微任务与 then 链 */
const flush = async () => {
  await nextTick();
  await nextTick();
  await nextTick();
};

/** 为 key 设置一个「永远阻塞」的任务，供手动放行 */
const setupBlockingTask = (key: any) => {