refactor(player): E.42 — migrate playerStore re-exports to direct imports (#607)

Migrates ~74 call sites away from the playerStore re-export shims that
were kept during M0–E.41 to avoid touching 30+ imports per PR. Now
that the bigger refactor work is done, each helper goes back to its
real home:

- `initAudioListeners`, `installQueueUndoHotkey`, `flushPlayQueuePosition`
  → from their own store modules
- `getPlaybackProgressSnapshot`, `subscribePlaybackProgress`,
  `PlaybackProgressSnapshot` → from `playbackProgress`
- `resolveReplayGainDb`, `shuffleArray`, `songToTrack`
  → from `utils/*`
- `_resetQueueUndoStacksForTest`, `consumePendingQueueListScrollTop`,
  `registerQueueListScrollTopReader` → from `queueUndo`
- `PlayerState`, `Track` types → from `playerStoreTypes`

Drops the corresponding 13 re-export stubs from `playerStore.ts` and
the now-unused imports. Also drops dead section banners + per-wrapper
comments above one-line action delegates. Trims one stale "(separate
PR)" note in `transportLightActions.ts` since that follow-up landed
in E.39.

`playerStore.ts`: 180 → 112 LOC (−68). Down from Phase E's starting
3732 LOC.

`bootstrap.test.ts` mock target updated from `../store/playerStore`
to `../store/queueUndoHotkey` to keep the spy reachable after the
import change.

src/pages/PlaylistDetail.tsx

@@ -1,3 +1,4 @@
+import { songToTrack } from '../utils/songToTrack';
 import React, { useEffect, useState, useRef, useCallback, useMemo } from 'react';
 import { createPortal } from 'react-dom';
 import { useParams, useNavigate, useLocation } from 'react-router-dom';
@@ -9,7 +10,7 @@ import {
   search, setRating, star, unstar,
   getRandomSongs, buildDownloadUrl, filterSongsToActiveLibrary, SubsonicPlaylist, SubsonicSong,
 } from '../api/subsonic';
-import { usePlayerStore, songToTrack } from '../store/playerStore';
+import { usePlayerStore } from '../store/playerStore';
 import { useShallow } from 'zustand/react/shallow';
 import { usePlaylistStore } from '../store/playlistStore';
 import { usePreviewStore } from '../store/previewStore';