~x-ai/grok-latest → A (3:1)

A adds a real domain subsystem (`url_rules` engine/registry) and redesigns `ItemId` around full canonical URLs with parent/breadcrumb rules and multi-site normalization (Reddit/YouTube), which is lasting core design. B mostly splits existing helpers into `canonical_path`/`identity`, drops `@` from wire forms, and makes delegate optional—valuable API hygiene, but largely reorganization plus contract tightening rather than new capability.