Bug: `until()` deadline counts time spent paused

[ZialeHub]

Description

The until() limit is checked as now - created_at >= limit. This uses wall-clock elapsed time from creation, which includes any time the task spent paused. Pausing a task therefore burns its until() budget,
causing it to expire earlier than intended.

Affected files

• src/scheduler/async_scheduler.rs — lines 67–70
• src/scheduler/sync_scheduler.rs — lines 67–70

Reproduction

  let id = scheduler.schedule(
      Box::new(task),
      every(1.seconds()).until(10.seconds()),
  ).unwrap();

  scheduler.pause(id).unwrap();
  std::thread::sleep(Duration::from_secs(9));
  scheduler.resume(id).unwrap();
  // Task now expires after ~1 more second of wall time, having barely run at all

Impact

A task configured to run "for 10 active seconds" will exit after 10 seconds of wall-clock time even if it was paused for 9 of those seconds.

Fix

Track the total paused duration and subtract it from the elapsed check:

  // In TaskDetails or the loop state:
  let effective_elapsed = (now - created_at) - total_paused_duration;
  if effective_elapsed.num_seconds() as u64 >= *limit { break; }

Or change the semantics to track an absolute stop-datetime computed at schedule time (analogous to until_datetime), so pause/resume don't affect it and the behavior is at least consistent and predictable
(document it clearly either way).