fix(queue): route scaffold masthead PLAY through queue; cache QueueItems snapshot

DeepDrftPublic.Client/Controls/AudioPlayerBar/AudioPlayerBar.razor.cs

@@ -85,13 +85,15 @@ public partial class AudioPlayerBar : ComponentBase, IAsyncDisposable
     // Gated on Fixed + non-empty so single-track embeds keep their compact, panel-free bar (UC6).
     private bool ShowFixedPanel => Fixed && HasQueue;
 
-    // Snapshot the live queue into a NEW list every render. QueueService.Items returns the service's
-    // backing list by reference, so passing it straight through means Blazor parameter diffing sees an
-    // unchanged reference after an in-place Clear/remove/reorder and the child (QueueList /
-    // MudDropContainer) keeps its stale snapshot until reopened (bug #4). Materializing a fresh list per
-    // access forces the parameter to change identity on every mutation, so the panel re-flows immediately.
+    // Cached snapshot of the queue list (bug #4 fix). QueueService.Items returns the service's
+    // backing list by reference, so passing it straight through means Blazor parameter diffing sees
+    // an unchanged reference after an in-place Clear/remove/reorder and the child (QueueList /
+    // MudDropContainer) keeps its stale snapshot until reopened. We snapshot on first access and
+    // rebuild in OnQueueChanged, so every real mutation hands the child a NEW reference while
+    // progress-tick re-renders (the frequent path) reuse the cached one without allocating.
+    private IReadOnlyList<TrackDto>? _queueItemsCache;
     private IReadOnlyList<TrackDto> QueueItems =>
-        QueueService is null ? [] : QueueService.Items.ToList();
+        _queueItemsCache ??= QueueService is null ? [] : QueueService.Items.ToList();
     private int QueueCurrentIndex => QueueService?.CurrentIndex ?? -1;
 
     // Fixed-mode panel collapse state (OQ1 Option A). Default expanded so a release embed shows the
@@ -147,6 +149,11 @@ public partial class AudioPlayerBar : ComponentBase, IAsyncDisposable
 
     private void OnQueueChanged()
     {
+        // Invalidate the snapshot so QueueItems rebuilds a fresh list on the next render.
+        // This gives Blazor a new reference on every real mutation (bug #4 reactivity preserved)
+        // while progress-tick re-renders that don't go through here keep the cached reference.
+        _queueItemsCache = null;
+
         // If a removal emptied the queue while the overlay was open, the button disappears (AC1) — close
         // the overlay so it cannot strand open over an empty queue. The button gate hides the overlay
         // mount too, so this keeps state and view consistent.

DeepDrftPublic.Client/Controls/ReleaseDetailScaffold.razor.cs

@@ -13,6 +13,7 @@ namespace DeepDrftPublic.Client.Controls;
 public partial class ReleaseDetailScaffold : ComponentBase
 {
     [CascadingParameter] public IStreamingPlayerService? PlayerService { get; set; }
+    [CascadingParameter] public IQueueService? Queue { get; set; }
 
     [Parameter] public required string Title { get; set; }
     [Parameter] public string? Artist { get; set; }
@@ -96,13 +97,19 @@ public partial class ReleaseDetailScaffold : ComponentBase
     {
         if (Track is null || PlayerService is null) return;
 
-        // Toggle if this track is already active (playing or paused); otherwise start a fresh
-        // stream. SelectTrackStreaming is the live entry point — the buffered path is dead.
+        // Toggle if this track is already active (playing or paused); 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 (prerender / non-interactive).
         var isThisTrack = PlayerService.CurrentTrack?.Id == Track.Id;
         if (isThisTrack && (PlayerService.IsPlaying || PlayerService.IsPaused))
         {
             await PlayerService.TogglePlayPause();
         }
+        else if (Queue is not null)
+        {
+            await Queue.PlayTrack(Track);
+        }
         else
         {
             await PlayerService.SelectTrackStreaming(Track);