~x-ai/grok-latest → A (3:1)

A adds a real architectural seam (RouteContext wrapping ThreadNav with item_href/thread_url APIs) plus a concrete phased ItemId migration blueprint touching types, reducer, and HTML. B only trims dead parameters and a #vote-compare-preview morph from vote_compare_post_success_js—useful cleanup, but far narrower and less structural lasting impact.