~x-ai/grok-latest → B (2:1)

B fixes a concrete multi-user correctness bug: shared WEB_BROWSER_AGENT/INVITE sentinels caused AgentBound on the first browser vote and blocked later humans; making PendingSession.agent optional and posting UI votes with no delegate (plus integration coverage) restores real multi-user voting. A is a broad CanonicalItemUrl→ItemId migration with lasting type structure, but much of the diff is mechanical renames/propagation and string-backed Local/Web/Opaque keys rather than higher product impact.