Ship the OpenAPIKit-style validation layer (builtin rules, warnings channel,
Validator tiers, coverage gates) and wire XSD compile checks through it. Advance
#161 with chameleon include validation, multi-container reference resolution,
and include targetNamespace composition rules so merged schema sets compile
correctly when a schemaLoader is provided.
A simple type whose final contains list (or #all) may not be a list itemType,
and one whose final contains union (or #all) may not be a union memberType.
finalRespected already covered restriction and extension; the list and union
directions were unchecked because the derivation-method set does not model
final="list"/"union", so the final attribute is read directly. The itemType /
memberTypes reference is matched only when it resolves to the schema's own target
namespace, so a list or union of a built-in (whose final is empty) is not
confused with a user type of the same local name. Checked for a self-contained
schema.
XSTS: invalid schemas accepted 413 to 411, no other bucket raised.
