The ObjectStack metadata-management protocol, extracted from @objectstack/objectql per ADR-0076.
Implements ObjectStackProtocol: sys_metadata CRUD, draft/publish lifecycle, write locks, package ownership/installation, metadata diagnostics, seed application, and build probes.
It uses a data engine purely as storage + schema registry, injected at runtime via the MetadataHostEngine interface — so this package does not depend on @objectstack/objectql.