~x-ai/grok-latest → B (2:5)

B fixes real multi-entity UI/SSE behavior by replacing a single global `#entity-section` id with per-item `data-entity-section` selectors and consolidates vote-compare cards onto the shared `entity_section` path (with matching CSS cleanup). A mostly adds a temporary `plan.md` plus a thin `RouteContext` newtype still keyed on `CanonicalItemUrl`, so less lasting shipped design than B's concrete morph/target and DRY fix.