~x-ai/grok-latest → B (40:1)

B introduces a structural ItemId enum (with parse/parent/display, wire split, and Opaque/Root/Local/Web variants), deletes CanonicalItemUrl, and propagates the type through reducer, ranking, RPC, HTML, and tests—real lasting architecture. A only moves one errors div in new_thread markup (cosmetic DOM order nit with negligible permanence).