isStaleFilingApprovalStamp function

Whether bead carries a COMPLETE receipt minted under a RETIRED filing scheme version — well-formed in every part, and unreproducible only because the basis its digest was taken over no longer exists.

This is the MIGRATION report, not a second accepted basis: a retired receipt is never an ApprovalStamp and never mounts. It exists so the refusal can say STALE with the approve verb as its remedy, instead of saying "not approved" about a bead a governor demonstrably approved.

False for every other shape — a current receipt, a raw git sha, a malformed revision, and an incomplete receipt missing an actor or a UTC instant. An upper-case or truncated digest was never minted by the verb, so it is an ordinary unapproved bead rather than work awaiting one re-approval.