Reference JavaScript implementation of the markstay spec (v1.2, parser-free core) with a stamp/lint CLI

mdast/remark adapter for markstay: §5.2 tree attachment, source-slice hashing, and intra-pipeline §11 enforcement

Emit an HTML id= per markstay stay so doc.md#stay-id deep links resolve in a browser

Fail-closed bridge between Plate's `withBlockId` serializer and markstay's stable block ids (carry Plate ids as invisible markstay markers, round-trip back). The optional `plate-stay/plugin` entry adds editor-native serialize/deserialize + drift detection