feat(queue): two-level deque model — PLAY prepends, add appends, last-track-end empties

Fixes five queue bugs: Playlist relabel, last-track-empties, dormant-seed-from-player on first add, immediate panel reactivity, and front/back deque semantics. Adds JumpTo for row jumps.

DeepDrftPublic.Client/Pages/SessionDetail.razor

@@ -94,10 +94,13 @@ else
     protected override string PersistKey => "session-detail";
 
     [CascadingParameter] public IStreamingPlayerService? PlayerService { get; set; }
+    [CascadingParameter] public IQueueService? Queue { get; set; }
 
     // Mirrors the play-toggle wiring the shared scaffold owns. Session detail composes the player
     // affordance directly (it diverges from ReleaseDetailScaffold for the overlay layout), so the
-    // toggle logic lives here: toggle if this track is already active, otherwise start a fresh stream.
+    // toggle logic lives here: toggle if this track is already active, otherwise PLAY it — prepend to
+    // the queue's front (deque PLAY semantics) so it becomes current and the existing queue stays
+    // intact behind it. Falls back to a direct stream when the queue cascade is absent.
     private async Task PlayTrack()
     {
         var track = ViewModel.Track;
@@ -108,6 +111,10 @@ else
         {
             await PlayerService.TogglePlayPause();
         }
+        else if (Queue is not null)
+        {
+            await Queue.PlayTrack(track);
+        }
         else
         {
             await PlayerService.SelectTrackStreaming(track);