Config validation#

Datum directly validates its closed configuration shape and mirrors the normative datum.schema.json. Direct validation remains a good fit while the surface is small: it keeps typed secret-reference checks explicit and makes runtime/schema parity testable without a general schema engine.

The schema documents, and runtime validation enforces, semantic constraints that draft 2020-12 cannot express directly: uniqueness by one object property, limits after durable and request arrays are composed, and UTF-8 byte limits owned by an imported Bearing contract. These are not independent Datum reinterpretations of ranking semantics.

This does not preserve ADR 0004 as a blanket zero-dependency rule. If the config surface grows enough that a maintained validator is safer or clearer, Datum may adopt one under the current Runtime dependencies decision. Config validation owns Datum config only; Bearing remains authoritative for Bearing catalog validation rather than being reimplemented here.