refactor(playlist): G.65 — extract Tracklist + FilterToolbar + displayedSongs (cluster) (#632)

Three-cut cluster on PlaylistDetail.tsx. 1065 → 742 LOC (−323).

PlaylistTracklist — the big one. Owns the bulk-action bar, column
visibility picker, sortable header (3-click cycle: asc → desc →
natural, plus arrow indicator + drag-resize handles between
columns), empty state with "add first song" button, and the song
rows themselves (drag-over indicators, current-track highlight,
bulk-selection check, ctrl/meta/shift selection vs. play vs.
orbit-queue-hint, inline play-next + preview buttons in the title
cell, artist/album links, star/rating cells, format/duration/delete
columns). Subscribes directly to playerStore (currentTrack /
isPlaying / playTrack / openContextMenu / starredOverrides /
userRatingOverrides), previewStore (previewingId / audioStarted),
themeStore (showBitrate), useDragDrop (isDragging),
useOrbitSongRowBehavior — so the parent doesn't have to thread any
of that through props. PL_CENTERED moves to the component because
the only remaining tracklist header lives there now.

PlaylistFilterToolbar — small filter input with clear-X.

playlistDisplayedSongs — pure `getDisplayedSongs(songs, opts)` that
returns the filtered + sorted song list. Exports PlaylistSortKey /
PlaylistSortDir types so PlaylistDetail's sortKey/sortDir state and
PlaylistTracklist's props share the same union types.

PlaylistDetail's import list loses the icons/components that only
the tracklist used (AudioLines, ChevronDown, Check, Heart,
RotateCcw, StarRating, AddToPlaylistSubmenu) — they followed the
component to the new file. Pure code move otherwise.

src/utils/playlistDisplayedSongs.ts

@@ -0,0 +1,43 @@
+import type { SubsonicSong } from '../api/subsonicTypes';
+
+export type PlaylistSortKey = 'natural' | 'title' | 'artist' | 'album' | 'favorite' | 'rating' | 'duration';
+export type PlaylistSortDir = 'asc' | 'desc';
+
+export interface DisplayedSongsOptions {
+  filterText: string;
+  sortKey: PlaylistSortKey;
+  sortDir: PlaylistSortDir;
+  ratings: Record<string, number>;
+  userRatingOverrides: Record<string, number>;
+  starredOverrides: Record<string, boolean>;
+  starredSongs: Set<string>;
+}
+
+export function getDisplayedSongs(songs: SubsonicSong[], opts: DisplayedSongsOptions): SubsonicSong[] {
+  const q = opts.filterText.trim().toLowerCase();
+  if (!q && opts.sortKey === 'natural') return songs;
+  let result = [...songs];
+  if (q) result = result.filter(s => s.title.toLowerCase().includes(q) || (s.artist ?? '').toLowerCase().includes(q));
+  if (opts.sortKey !== 'natural') {
+    result.sort((a, b) => {
+      let av: string | number;
+      let bv: string | number;
+      const effectiveRating = (s: SubsonicSong) => opts.ratings[s.id] ?? opts.userRatingOverrides[s.id] ?? s.userRating ?? 0;
+      const effectiveStarred = (s: SubsonicSong) => (s.id in opts.starredOverrides ? opts.starredOverrides[s.id] : opts.starredSongs.has(s.id)) ? 1 : 0;
+      switch (opts.sortKey) {
+        case 'title': av = a.title; bv = b.title; break;
+        case 'artist': av = a.artist ?? ''; bv = b.artist ?? ''; break;
+        case 'album': av = a.album ?? ''; bv = b.album ?? ''; break;
+        case 'favorite': av = effectiveStarred(a); bv = effectiveStarred(b); break;
+        case 'rating': av = effectiveRating(a); bv = effectiveRating(b); break;
+        case 'duration': av = a.duration ?? 0; bv = b.duration ?? 0; break;
+        default: av = a.title; bv = b.title;
+      }
+      if (typeof av === 'number' && typeof bv === 'number') {
+        return opts.sortDir === 'asc' ? av - bv : bv - av;
+      }
+      return opts.sortDir === 'asc' ? (av as string).localeCompare(bv as string) : (bv as string).localeCompare(av as string);
+    });
+  }
+  return result;
+}