~x-ai/grok-latest → B (2:1)

B adds an executable browser test that seeds a pool, drives the vote→next-pair loop, and asserts pool-scoped pairs and edge-history updates—lasting regression coverage of real product behavior. A mostly adds a temporary plan.md plus a thin RouteContext newtype that delegates to ThreadNav without migrating call sites or introducing ItemId, so its durable code impact is smaller.