Type the approval denial helper with a closed ApprovalErrorCode, state
that a cancellation is recognized by the signal reason or an Error named
AbortError, note that ApprovalError names a denial rather than a thrown
class, and separate JOB_CONTROLLER_UNAVAILABLE from a missing jobs
service. The jobs README describes JobError as the seam's export rather
than as current caller behavior, and the terminal test asserts one
concurrent send failure.
Refs #7869
sjw1231
09604ac04d