QueueServiceSlotFailureTests's throwing-slot test broke its poll loop the
instant the DB read observed Status==Failed, but TaskStateService.FailAsync
commits the status flip before calling the broadcaster's TaskUpdated, so the
assertion could race ahead of the broadcast landing in hub.Proxy.Calls
(~1-in-5 failures in isolation). Wait for both signals before breaking.
RunInSlotAsync only logged an unexpected exception, leaving a task stuck
Running in the DB forever with the UI never notified (the raw-SQL queue
claim that put it there never broadcasts). Cancellation is handled
separately and left alone, since the cancel path already wrote the
terminal status.