The probe and re-probe worker delegates closed over the CTS and read cts.Token
when they ran. Task.Run's scheduling token only suppresses a still-queued task;
a worker the pool had committed to but not yet invoked could outlive the bounded
join in StopBackgroundLoopsAsync, after which the CTS was disposed and the
delayed cts.Token read threw ObjectDisposedException (faulting the loop task).
Snapshot the token value before Task.Run and close over it; a token value stays
valid after its source is disposed and still reports cancellation, so a late
worker exits cleanly on its own generation's cancelled token. Document the
bounded-join / transport-lifetime limits on StopBackgroundLoopsAsync.
Regression tests park the worker deterministically in TPL's synchronous
TaskStarted event (after the start check, before the delegate runs) via an
EventListener correlated to the one TaskScheduled on the test's armed flow:
shutdown (probe + reprobe) and replacement-generation identity. All three fail
with ObjectDisposedException without the fix.
Joseph Doherty
66867ca8f6