fix(music): playlist tracks replaced each other instead of queueing

- TrackScheduler: track current track locally instead of relying on
  async-cached LavalinkPlayer.getTrack(); playlist enqueues now queue
  instead of REPLACED-storming (only last track was audible)
- TrackEndHandler: ignore REPLACED/STOPPED (intentional), advance on
  FINISHED/LOAD_FAILED via nextTrack(), log CLEANUP
- TrackStarter: preserve player volume between tracks instead of
  hardcoding 100; report final failure to scheduler
- skip(): start next track atomically (single player update), support
  skipping several tracks; prefix skip N no longer stops playback
- QueueStore: restore queue through scheduler.enqueue
- TrackScheduler ops synchronized (queue mutated from reactor + JDA
  threads)
- syncCurrent on TrackStartEvent as authoritative source

src/main/java/creator/loki/feature/music/commands/control/SkipCommand.java

@@ -52,10 +52,7 @@ final class SkipCommand implements Command {
       }
     }
     String skipped = manager.getScheduler().getCurrentTrack().getInfo().getTitle();
-    for (int i = 0; i < amount - 1; i++) {
-      manager.getScheduler().nextTrack();
-    }
-    manager.getScheduler().skip();
+    manager.getScheduler().skip(amount);
     context
         .getChannel()
         .sendMessageEmbeds(EmbedTemplates.info("Пропущено", "**" + skipped + "**"))

src/main/java/creator/loki/feature/music/core/LavalinkEventRouter.java

@@ -51,6 +51,7 @@ class LavalinkEventRouter {
             event -> {
               GuildMusicManager manager = musicManagers.get(event.getGuildId());
               if (manager != null) {
+                manager.getScheduler().syncCurrent(event.getTrack());
                 manager.cancelAutoLeaveTimer();
               }
             });

src/main/java/creator/loki/feature/music/manage/player/QueueStore.java

@@ -61,14 +61,8 @@ class QueueStore {
     if (decoded.isEmpty()) {
       return;
     }
-    var q = manager.getScheduler().queue;
-    q.addAll(decoded.subList(1, decoded.size()));
-    var first = decoded.get(0);
-    var player = manager.getPlayer().orElse(null);
-    if (player != null && player.getTrack() == null) {
-      manager.getScheduler().startTrack(first);
-    } else {
-      q.offer(first);
+    for (var track : decoded) {
+      manager.getScheduler().enqueue(track);
     }
     LoggerDecorator.music(logger, "Восстановлено " + decoded.size() + " треков");
     queueRepository.deleteQueue(String.valueOf(manager.getGuildId()));

src/main/java/creator/loki/feature/music/manage/player/TrackEndHandler.java

@@ -18,38 +18,33 @@ class TrackEndHandler {
   }
 
   void onTrackEnd(final Track lastTrack, final AudioTrackEndReason endReason) {
-    if (endReason == AudioTrackEndReason.LOAD_FAILED) {
-      handleLoadFailed();
-    } else if (!endReason.getMayStartNext() && endReason != AudioTrackEndReason.FINISHED) {
-      handleUnexpectedEnd(endReason);
-    } else if (scheduler.isRepeating() && endReason == AudioTrackEndReason.FINISHED) {
-      handleFinished(lastTrack);
-    } else {
-      nextOrAutoLeave();
+    switch (endReason) {
+      case LOAD_FAILED -> handleLoadFailed();
+      case FINISHED -> handleFinished(lastTrack);
+      case REPLACED, STOPPED -> {
+        // Track was intentionally replaced or stopped by skip()/stop(); the scheduler
+        // already advanced playback, so there is nothing to do here.
+      }
+      case CLEANUP -> handleCleanedUp();
     }
   }
 
   private void handleLoadFailed() {
     LoggerDecorator.warn(log, "Load failed, skipping to next");
     scheduler.notifyLoadFailed();
-    nextOrAutoLeave();
-  }
-
-  private void handleUnexpectedEnd(final AudioTrackEndReason endReason) {
-    LoggerDecorator.warn(log, "Track ended unexpectedly: " + endReason);
-    manager.startAutoLeaveTimer();
+    scheduler.nextTrack();
   }
 
   private void handleFinished(final Track lastTrack) {
-    scheduler.startTrack(lastTrack.makeClone());
-  }
-
-  private void nextOrAutoLeave() {
-    var next = scheduler.pollNext();
-    if (next != null) {
-      scheduler.startTrack(next);
+    if (scheduler.isRepeating()) {
+      scheduler.startTrack(lastTrack.makeClone());
     } else {
-      manager.startAutoLeaveTimer();
+      scheduler.nextTrack();
     }
   }
+
+  private void handleCleanedUp() {
+    LoggerDecorator.warn(log, "Player cleaned up (node restart?), stopping session");
+    manager.startAutoLeaveTimer();
+  }
 }

src/main/java/creator/loki/feature/music/manage/player/TrackScheduler.java

@@ -8,7 +8,6 @@ import java.util.Queue;
 import java.util.function.Consumer;
 
 import creator.loki.feature.music.manage.filter.FilterState;
-import dev.arbjerg.lavalink.client.player.LavalinkPlayer;
 import dev.arbjerg.lavalink.client.player.Track;
 import dev.arbjerg.lavalink.protocol.v4.Message.EmittedEvent.TrackEndEvent.AudioTrackEndReason;
 import org.slf4j.Logger;
@@ -22,6 +21,7 @@ public class TrackScheduler {
   private final TrackStarter trackStarter;
   private final TrackEndHandler trackEndHandler;
   final Queue<Track> queue = new LinkedList<>();
+  private Track current;
   private boolean repeating;
   public final FilterState filterState = new FilterState();
   private Consumer<String> onLoadFailedNotify;
@@ -38,49 +38,78 @@ public class TrackScheduler {
 
   public void enqueue(final Track track) {
     manager.cancelAutoLeaveTimer();
-    if (manager.getPlayer().filter(p -> p.getTrack() != null).isPresent()) {
+    synchronized (this) {
       queue.offer(track);
-      manager.saveQueueDebounced();
-    } else {
-      startTrack(track);
+      if (current == null) {
+        nextTrack();
+      } else {
+        manager.saveQueueDebounced();
+      }
     }
   }
 
   public void skip() {
-    manager.getPlayer().ifPresent(p -> p.setTrack(null).subscribe(null, LOG_LAV));
+    skip(1);
+  }
+
+  public void skip(final int amount) {
+    synchronized (this) {
+      for (int i = 0; i < amount - 1 && !queue.isEmpty(); i++) {
+        queue.poll();
+      }
+      var next = queue.poll();
+      if (next != null) {
+        startTrack(next);
+      } else {
+        stopPlayback();
+        manager.startAutoLeaveTimer();
+      }
+      manager.saveQueueDebounced();
+    }
   }
 
   public boolean nextTrack() {
-    var next = queue.poll();
-    if (next == null) {
-      return false;
+    synchronized (this) {
+      var next = queue.poll();
+      if (next == null) {
+        current = null;
+        manager.startAutoLeaveTimer();
+        return false;
+      }
+      startTrack(next);
+      manager.saveQueueDebounced();
+      return true;
     }
-    startTrack(next);
-    manager.saveQueueDebounced();
-    return true;
   }
 
   public void stop() {
-    manager.cancelAutoLeaveTimer();
-    queue.clear();
-    manager.getPlayer().ifPresent(p -> p.setPaused(false).setTrack(null).subscribe(null, LOG_LAV));
-    manager.saveQueue();
+    synchronized (this) {
+      manager.cancelAutoLeaveTimer();
+      queue.clear();
+      stopPlayback();
+      current = null;
+      manager.saveQueue();
+    }
   }
 
   public void shuffle() {
-    var list = new ArrayList<>(queue);
-    Collections.shuffle(list);
-    queue.clear();
-    queue.addAll(list);
-    manager.saveQueueDebounced();
+    synchronized (this) {
+      var list = new ArrayList<>(queue);
+      Collections.shuffle(list);
+      queue.clear();
+      queue.addAll(list);
+      manager.saveQueueDebounced();
+    }
   }
 
   public List<Track> getQueue() {
-    return List.copyOf(queue);
+    synchronized (this) {
+      return List.copyOf(queue);
+    }
   }
 
   public Track getCurrentTrack() {
-    return manager.getPlayer().map(LavalinkPlayer::getTrack).orElse(null);
+    return current;
   }
 
   public boolean isRepeating() {
@@ -117,8 +146,23 @@ public class TrackScheduler {
 
   void startTrack(final Track track) {
     manager.cancelAutoLeaveTimer();
+    current = track;
     var link = manager.getLavalinkManager().getOrCreateLink(manager.getGuildId());
-    trackStarter.startWithRetry(link, track);
+    trackStarter.startWithRetry(
+        link,
+        track,
+        () -> {
+          synchronized (this) {
+            if (current == track) {
+              current = null;
+            }
+          }
+          manager.startAutoLeaveTimer();
+        });
+  }
+
+  public void syncCurrent(final Track track) {
+    current = track;
   }
 
   void notifyLoadFailed() {
@@ -127,7 +171,8 @@ public class TrackScheduler {
     }
   }
 
-  Track pollNext() {
-    return queue.poll();
+  private void stopPlayback() {
+    manager.getPlayer().ifPresent(p -> p.setPaused(false).setTrack(null).subscribe(null, LOG_LAV));
+    current = null;
   }
 }

src/main/java/creator/loki/feature/music/manage/player/TrackStarter.java

@@ -3,6 +3,7 @@ package creator.loki.feature.music.manage.player;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 
+import creator.loki.feature.music.util.voice.VolumeControl;
 import dev.arbjerg.lavalink.client.Link;
 import dev.arbjerg.lavalink.client.player.Track;
 import org.slf4j.Logger;
@@ -11,8 +12,7 @@ import org.slf4j.LoggerFactory;
 class TrackStarter {
   private static final Logger log = LoggerFactory.getLogger(TrackStarter.class);
   private static final int MAX_ATTEMPTS = 5;
-  private static final long RETRY_DELAY_PLAYER_NULL_MS = 300;
-  private static final long RETRY_DELAY_SUBSCRIBE_ERROR_MS = 500;
+  private static final long RETRY_DELAY_MS = 500;
 
   private final ScheduledExecutorService executor;
 
@@ -25,24 +25,29 @@ class TrackStarter {
    *
    * @param link the Lavalink link to play the track on
    * @param track the track to start
+   * @param onFinalFailure invoked when all attempts are exhausted
    */
-  void startWithRetry(final Link link, final Track track) {
-    startWithRetry(link, track, 0);
+  void startWithRetry(final Link link, final Track track, final Runnable onFinalFailure) {
+    startWithRetry(link, track, 0, onFinalFailure);
   }
 
-  private void startWithRetry(final Link link, final Track track, final int attempt) {
+  private void startWithRetry(
+      final Link link, final Track track, final int attempt, final Runnable onFinalFailure) {
     if (attempt > MAX_ATTEMPTS) {
+      if (onFinalFailure != null) {
+        onFinalFailure.run();
+      }
       return;
     }
     link.createOrUpdatePlayer()
         .setTrack(track)
-        .setVolume(100)
+        .setVolume(VolumeControl.current(link))
         .subscribe(
             null,
             err ->
                 executor.schedule(
-                    () -> startWithRetry(link, track, attempt + 1),
-                    RETRY_DELAY_SUBSCRIBE_ERROR_MS,
+                    () -> startWithRetry(link, track, attempt + 1, onFinalFailure),
+                    RETRY_DELAY_MS,
                     TimeUnit.MILLISECONDS));
   }
 }

src/test/java/creator/loki/feature/music/manage/player/TrackSchedulerTest.java

@@ -40,39 +40,87 @@ class TrackSchedulerTest {
   }
 
   @Test
-  void enqueue_addsTrackToEmptyPlayer() {
-    when(manager.getPlayer()).thenReturn(java.util.Optional.empty());
-
+  void enqueue_startsTrackWhenIdle() {
     var track = mock(Track.class);
+
     scheduler.enqueue(track);
 
+    assertSame(track, scheduler.getCurrentTrack());
     verify(manager, times(2)).cancelAutoLeaveTimer();
     verify(lavalinkManager).getOrCreateLink(123L);
   }
 
   @Test
-  void enqueue_addsTrackToQueueWhenPlayerBusy() {
-    when(player.getTrack()).thenReturn(mock(Track.class));
-    when(manager.getPlayer()).thenReturn(java.util.Optional.of(player));
+  void enqueue_playlistOnlyStartsFirstTrack() {
+    for (int i = 0; i < 5; i++) {
+      scheduler.enqueue(mock(Track.class));
+    }
 
-    var track = mock(Track.class);
-    scheduler.enqueue(track);
-
-    assertEquals(1, scheduler.queue.size());
-    assertSame(track, scheduler.queue.peek());
-    verify(manager).cancelAutoLeaveTimer();
-    verify(manager).saveQueueDebounced();
+    assertNotNull(scheduler.getCurrentTrack());
+    assertEquals(4, scheduler.queue.size());
+    verify(lavalinkManager, times(1)).getOrCreateLink(123L);
+    verify(manager, atLeastOnce()).saveQueueDebounced();
   }
 
   @Test
-  void skip_clearsCurrentTrack() {
-    when(manager.getPlayer()).thenReturn(java.util.Optional.of(player));
-    when(player.setTrack(null)).thenReturn(builder);
+  void enqueue_addsTrackToQueueWhenAlreadyPlaying() {
+    var playing = mock(Track.class);
+    var queued = mock(Track.class);
+
+    scheduler.enqueue(playing);
+    scheduler.enqueue(queued);
+
+    assertEquals(1, scheduler.queue.size());
+    assertSame(queued, scheduler.queue.peek());
+    verify(manager, atLeastOnce()).saveQueueDebounced();
+  }
+
+  @Test
+  void skip_startsNextTrackFromQueue() {
+    var playing = mock(Track.class);
+    var next = mock(Track.class);
+    scheduler.enqueue(playing);
+    scheduler.enqueue(next);
 
     scheduler.skip();
 
-    verify(player).setTrack(null);
-    verify(builder).subscribe(any(), any());
+    assertSame(next, scheduler.getCurrentTrack());
+    assertEquals(0, scheduler.queue.size());
+    verify(lavalinkManager, times(2)).getOrCreateLink(123L);
+  }
+
+  @Test
+  void skip_skipsSeveralTracks() {
+    scheduler.enqueue(mock(Track.class));
+    scheduler.enqueue(mock(Track.class));
+    var target = mock(Track.class);
+    scheduler.enqueue(target);
+
+    scheduler.skip(2);
+
+    assertSame(target, scheduler.getCurrentTrack());
+  }
+
+  @Test
+  void skip_clearsCurrentTrackWhenQueueEmpty() {
+    when(manager.getPlayer()).thenReturn(java.util.Optional.of(player));
+    when(player.setPaused(false)).thenReturn(builder);
+    when(player.setTrack(null)).thenReturn(builder);
+
+    scheduler.enqueue(mock(Track.class));
+    scheduler.skip();
+
+    assertNull(scheduler.getCurrentTrack());
+    verify(builder).setTrack(null);
+    verify(builder, times(2)).subscribe(any(), any());
+    verify(manager).startAutoLeaveTimer();
+  }
+
+  @Test
+  void nextTrack_emptyQueueStartsAutoLeave() {
+    assertFalse(scheduler.nextTrack());
+    assertNull(scheduler.getCurrentTrack());
+    verify(manager).startAutoLeaveTimer();
   }
 
   @Test
@@ -86,6 +134,7 @@ class TrackSchedulerTest {
     scheduler.stop();
 
     assertTrue(scheduler.queue.isEmpty());
+    assertNull(scheduler.getCurrentTrack());
     verify(manager).cancelAutoLeaveTimer();
     verify(manager).saveQueue();
     verify(builder).subscribe(any(), any());