Variable: DEAD_LETTER_AT
const DEAD_LETTER_AT: "9999-12-31T23:59:59.999Z" = '9999-12-31T23:59:59.999Z';
Defined in: backoff.ts:22
nextAttemptAt for an op that must never be retried automatically again.
The frozen OutboxQueue.fail takes a required ISO string, so "dead" is
expressed as an attempt time that can never come due (docs/10 §4.7).