ADR-0087 exemption (no-migration-prescription): Nothing authorable moves: `precision` keeps its key, its type (`z.number().int().min(0)`) and its legality on every field type, and no stored metadata representation changes, so `objectstack migrate meta` has nothing to rewrite and the ledger has no row to gain. What narrows is the record validator's write accept set for values under an already-declared count, which is runtime behaviour, not an authored shape. The spec edits add a member to a closed enum, two message templates and a describe; none removes or renames anything an author can write. The other categories are closed on facts: both packages publish (not `unpublished`); no ADR-0087 id is minted here and none covers this (not `registered` / `already-registered`); and runtime behaviour changes, not only a TypeScript declaration (not `runtime-interface-only` / `type-surface-only`).