ADR-0087 exemption (no-migration-prescription): An accept-set narrowing performed entirely at the runtime boot path: `PluginSchema` is READ by `kernel.use()`, not changed. No metadata key, spec symbol, Zod schema, object definition or stored representation is added, removed or given a different name, so `objectstack migrate meta` has nothing to visit and there is no tombstone to mint. Stored metadata is untouched; what moves is which plugin OBJECTS a boot accepts. The channel that reaches an affected plugin author is the refusal itself, which names the offending key at `kernel.use()` and is more precise than a ledger line — and which value a formerly-refused key should carry is authoring intent no ledger entry can decide.