Start the plaintext scrub of a firm's old rows, one job per member (operators only)

Clears the plaintext twin of each sealed value written before the sealed copies were the only ones: an entry's judged copy becomes the empty object and an old interval's summary and label become null, each only where the sealed value opens to the same content. Refused with 409 while a release older than this one may still be served. Idempotent.