Add queue Move/RemoveAt + dormant-Enqueue coherence and shared QueueList (Phase 17.1)

DeepDrftPublic.Client/Services/IQueueService.cs

@@ -87,12 +87,45 @@ public interface IQueueService
     /// </summary>
     Task Start();
 
-    /// <summary>Appends a track to the end of the queue without changing what is currently playing.</summary>
+    /// <summary>
+    /// Appends a track to the end of the queue without changing what is currently playing.
+    /// Into a dormant queue (<see cref="CurrentIndex"/> == -1) the append leaves a coherent
+    /// <see cref="CurrentIndex"/> (the first appended track) so a subsequent play/skip is correct —
+    /// but it does NOT begin playback (add is not play). Interop-free; safe during prerender.
+    /// </summary>
     void Enqueue(TrackDto track);
 
-    /// <summary>Appends tracks to the end of the queue without changing what is currently playing.</summary>
+    /// <summary>
+    /// Appends tracks to the end of the queue without changing what is currently playing.
+    /// Into a dormant queue (<see cref="CurrentIndex"/> == -1) the append leaves a coherent
+    /// <see cref="CurrentIndex"/> (the first appended track) so a subsequent play/skip is correct —
+    /// but it does NOT begin playback (add is not play). Interop-free; safe during prerender.
+    /// </summary>
     void EnqueueRange(IEnumerable<TrackDto> tracks);
 
+    /// <summary>
+    /// Reorders the queue, moving the track at <paramref name="fromIndex"/> to
+    /// <paramref name="toIndex"/>, and re-emits <see cref="QueueChanged"/>. Adjusts
+    /// <see cref="CurrentIndex"/> so the <em>same track</em> stays current across the move — it does
+    /// not restart, re-stream, or interrupt the currently-playing track. Interop-free; safe during
+    /// prerender. No-op (no throw, no <see cref="QueueChanged"/>) when either index is out of range
+    /// or the indices are equal.
+    /// </summary>
+    void Move(int fromIndex, int toIndex);
+
+    /// <summary>
+    /// Removes the track at <paramref name="index"/> and re-emits <see cref="QueueChanged"/>. Does
+    /// not touch playback (the player stays a single-track device): removing the current track does
+    /// not stop it — the playing track runs to its natural end while <see cref="CurrentIndex"/>
+    /// resolves to the new occupant of that slot (the next track) so the next auto-advance/skip is
+    /// coherent. Removing a track before the current decrements <see cref="CurrentIndex"/> (the same
+    /// track stays current); removing after the current leaves it unchanged. Removing the last
+    /// remaining track empties the queue (<see cref="CurrentIndex"/> == -1, dormant). Interop-free;
+    /// safe during prerender. No-op (no throw, no <see cref="QueueChanged"/>) when
+    /// <paramref name="index"/> is out of range.
+    /// </summary>
+    void RemoveAt(int index);
+
     /// <summary>
     /// Advances to the next track and streams it. No-op when <see cref="HasNext"/> is false.
     /// </summary>