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
