ADR-0087 exemption (no-migration-prescription): A validity narrowing over existing keys: no key is removed, renamed or re-shaped, so there is no tombstone and nothing mechanical for `objectstack migrate meta` to rewrite. The parse refusal is the channel that reaches an affected author, at the parse site, carrying the remedy; whether an inert wizard-step `visibleWhen` meant "move it onto the fields" or "delete the leftover" is authoring intent no migration entry can decide on an upgrader's behalf — and the measured population of affected sources is zero in every corpus. Mirrors the disposition of the #11519 / #11842 ActionSchema narrowings.