Two invariants weren't captured by the wiki or the review-architecture skill, so a PR could break them and pass review: - node-schemas.md documented no backward-compat rule, even though migrateNodes() runs at load. Add a Schema Evolution section (new fields need a Zod default; renames/removals/retypes need a migrateNodes entry) plus a Rules bullet. - review-architecture skill only checked the narrow host-children case for migrations and had no editor-layer check at all. Add a general schema-migration item (§B) and an editor-overlay-layer item (§E, overlay meshes must set EDITOR_LAYER or they leak into thumbnails/snapshots and the ink/SSGI buffers). Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>