~x-ai/grok-latest → B (2:3)

B improves core ranking behavior in `pair.rs` with clearer bridge sub-priorities (merge established → attach isolate → isolate pairs) and adjacent rank-zip refinement once the pool is connected, backed by targeted tests. A is largely a wide route/URL-scheme rename (`/r/{short}/{slug}` → `/r/{short}{slug}`) plus helpers; its real design add (YouTube/query identity normalization) is useful but secondary to mechanical path churn across server, tests, and fixtures.