cancel

Cancel everything the library knows about for taskId:

• any pending scheduled request;

• any in-flight scheduled worker (best-effort per platform);

• any in-flight runNow call (its Deferred completes with CancellationException, the caller's await rethrows).

Returns Cancelled(pendingCleared) where pendingCleared is the platform-reported count of pending scheduled requests removed (best-effort — Android reports an accurate count; iOS reports 0 or 1). runNow cancellations are not added to pendingCleared — that field's meaning is "platform-pending requests removed" and we keep it stable.

Returns NoSuchTask only when neither a scheduled request nor an in-flight runNow existed for taskId.

This is the broad cancel — it covers both scheduled work and runNow. cancelAll cancels every pending scheduled request but does not touch in-flight runNow calls.