Why a COMPLETED job delivered no document.
Read for what a run did; the verdict only says whether anything was lost. A run whose
source handed back nothing finishes processing_status: SUCCESS with an empty
destination, and without this there is no statement anywhere that it moved nothing
(Pylon 2287, PLU-622). A run that discovered documents and delivered none of them
without failing any is FAILED, and carries this for the same reason: nothing else on the
row explains it. A run whose documents failed carries none of these; /failed-files
explains it.
So the verdict cannot be used to find these runs, and a caller that wants to know
whether a job delivered anything branches on this field.
Its own type on its own nullable field, deliberately NOT a JobProcessingStatus
member: that enum is on the public wire and a closed generated-SDK enum breaks a
whole list_jobs page on one unrecognised value (DTPL-696, REJECTED).
Null is "no issue detected", never "checked and fine" -- a caller must not read the
absence of a value as a guarantee, and a job FAILED for some other reason (a failed
document, a preflight rejection) carries none of these. New members may be added; treat
an unrecognised one as "an issue was detected, of a kind this client does not know".