ADR-0087 exemption (no-migration-prescription): A boot-time refusal in `os serve`: no key of any metadata schema is removed, renamed or re-shaped, so there is nothing for `objectstack migrate meta` to rewrite and no tombstone. No export, type, flag or error code is removed or renamed. The remedy is a deployment one (repair the install), stated below. The other categories are closed on facts: the package publishes (not unpublished); no ADR-0087 id covers this boot (not registered or already-registered); and nothing exported is removed or narrowed (not runtime-interface-only, type-surface-only or runtime-export-retired).