Validate an artifact's invariants and return it frozen. Called by every
accept function; call it directly when constructing an artifact by hand.
Enforced: contract version, identity shape, unique mark keys, the mark
ceiling, message presence for unsupported / error, declared ordering
actually holding, and histogram/time-series bucket monotonicity.
Validate an artifact's invariants and return it frozen. Called by every accept function; call it directly when constructing an artifact by hand.
Enforced: contract version, identity shape, unique mark keys, the mark ceiling,
messagepresence forunsupported/error, declared ordering actually holding, and histogram/time-series bucket monotonicity.