/** Request completion is normal; premature response closure cancels dependent work. */
export function requestLifetime(req, res) {
  const controller = new AbortController();
  const abort = () => controller.abort();
  const closed = () => {if (!res.writableFinished) abort();};
  req.once('aborted',abort);res.once('close',closed);
  if(req.aborted || res.destroyed) abort();
  return {signal:controller.signal,dispose(){req.off('aborted',abort);res.off('close',closed);}};
}