ADR-0087 exemption (no-migration-prescription): A TypeScript narrowing on a published runtime interface, aligning `packages/core` to the accept set `packages/spec` already declared. No metadata key, spec symbol, Zod schema, object definition or stored representation is added, removed or renamed — `CORE_PLUGIN_TYPES` and `PluginSchema.type` are read, not changed — so `objectstack migrate meta` has nothing to rewrite and there is no tombstone to mint. The channel that reaches an affected author is the compiler, at the assignment, which is more precise than a ledger line; which member a formerly `string`-typed value should become is authoring intent no migration entry can decide. The in-repo census under the workspace typecheck is recorded on the PR.