v7.83.1

Pairs with engine-service-v0.1.162, unchanged from 7.83.0. 7.83.0 was tagged but never published: the release workflow's engine-floor check refused it because the data-effect relay attestation for engine-service-v0.1.162 (docs/data-effect-relay/engine-service-v0.1.162.json, the record that the vectors-036-1 drop was relayed to the cloud operator) was committed to develop and not to the tagged tree. 7.83.1 is the 7.83.0 tree plus that file; there is no code change. Install 7.83.1; the 7.83.0 notes below describe what it contains.