Historical / legacy documentation — design history, lineage, deprecated approaches, and pre-Hyperon (OpenCog-era) context. Buried by design: read-restricted to elevated roles (Expert / Editor / Raw Data Analyst / Administrator) and never included, indexed in the sidebar/TOCs, or surfaced in search, so students and basic-role agents don't accidentally encounter confusing legacy material. Reached only via an explicit "History" link on the corresponding FULL card.