Prove a whole run of payments settled, one signed receipt per transaction

Up to 20 settlement attestations in one purchase. Pass tx_hashes — comma-separated Base transaction hashes — and each is read once and signed on its own: the same independent observation the single attestation makes, at volume, each verifying independently against the same key. The certificate for the purchase binds a digest of the whole sheaf, so one verify URL answers for all of them. Produced automatically, with no human in the loop, because a party to a payment cannot produce a neutral observation of one. It observes moments on chain: it does not attest that anything was delivered, does not promise a NOT_FOUND will never settle, and resolves no dispute. Delivered in the response.