fix(playlist): sorting a column no longer snaps the viewport (#840) (#848)

* fix(playlist): sorting a column no longer snaps the viewport (#840)

Sorting flipped `isFiltered` (which means displayedSongs !== songs, so it
also goes true once a sort is active), and the scroll-to-list effect fired
on `[id, isFiltered]` → the viewport snapped down to the list. Drive that
effect from a dedicated `hasActiveFilter` (filter text only), so sorting
applies in place; filter and playlist-switch scrolling are unchanged.

* docs(changelog): playlist sort viewport fix (#848)

src/pages/PlaylistDetail.tsx

@@ -349,6 +349,7 @@ export default function PlaylistDetail() {
         displayedSongs={displayedSongs}
         displayedTracks={displayedTracks}
         isFiltered={isFiltered}
+        hasActiveFilter={filterText.trim().length > 0}
         id={id}
         sortKey={sortKey}
         setSortKey={setSortKey}