creationZone property
The zone the job was created in, where an unobserved failure of the job goes when no observer answers for it.
An engine that starts a job later, from a queue, starts it here, as
creationZone.run(start): the queue runs in the zone of whatever woke
it, and a body started from there takes that zone's timers, values
and error handler for its own.
For a job made inside the work of JobContext.unattended this is the zone that work was started from, the one start moves to out of the fork; when the work of one job runs inside the work of another, it is the zone the outer work was started from. It is not the fork, the zone current at creation: the fork carries the job that started the work, and an engine that kept it would hold that job for as long as it kept the fork.
Implementation
@protected
Zone get creationZone => _zone;