The feed's bespoke select + asc/desc button is now the generic SortControl,
fed a SortOption[] built from the feed vocabulary (relevance offered only with
a query; shuffle/relevance directionless). The feedSort wire codec
(parseSort/buildSort) stays as the server-boundary translation, and the
reshuffle button rides SortControl's `trailing` slot so shuffle keeps its
re-seed affordance. Behaviour-equivalent; ArrowUp/ArrowDown imports dropped.