Immutable snapshot value types encoding the frontmatter tables: ItemID wraps the exact folder name (not Foundation UUID, which uppercases); lanes/cards carry FieldValue-typed fields, display-ordered children including flagged tombstones, and their full FrontmatterDocument so unknown and reserved keys ride along uninterpreted. Boards are identified by rootURL — package folders are human-named, not UUIDs. Claude-Session: https://claude.ai/code/session_018BjQRYBR6jQja3jCRi5S3A