ADR-0087 exemption (no-migration-prescription): a runtime refusal on one REST route: the external-table import now relays the metadata door's own save refusals (a destructive re-import, a name that door will not overwrite) as 400 where it answered 201 with an in-memory write no restart kept. No authorable metadata key, spelling, export, config field or stored shape moves: no schema changes, no sys_metadata row is read or rewritten, and which table or name an operator meant to re-import is not something a ledger entry can rewrite. The validation half refuses less, not more. The other categories are closed on facts: @objectstack/service-datasource publishes (not unpublished); no ADR-0087 id covers this route (not already-registered); and the change is a runtime verdict, not a declaration (not runtime-interface-only or type-surface-only).