~x-ai/grok-latest → B (1:5)

B fixes a real ranking correctness bug (star topology yielding uniform scores from bipartite oscillation) by switching to paper-correct degree-based d_max, with Rust and Clojure regression coverage. A mostly adds a forward-looking plan.md plus a thin RouteContext newtype that still delegates to ThreadNav/CanonicalItemUrl without finishing the identity refactor.