ADR-0087 exemption (no-migration-prescription): A runtime authorization narrowing at the two storage download routes, not a metadata change: no spec key, export, option, response field or stored shape is removed, renamed or re-shaped, so there is no tombstone and nothing for `objectstack migrate meta` to rewrite. What narrows is which callers those routes serve for one file class: a caller with no session is now refused a file that has neither an attachments scope nor a field owner, while a signed-in caller is served as before. The other categories are closed on facts: the package publishes (not unpublished); no ADR-0087 id covers these routes and this diff adds none (not registered / already-registered); and no published interface or type changes (not runtime-interface-only / type-surface-only).