Add whole-release embeds to FramePlayer and un-gate the release embed share affordance

The queue gains an armed-but-idle state (Arm/Start) so a release embed stages track 0 prerender-safe, then queues the full release on first play and auto-advances.

DeepDrftTests/QueueServiceTests.cs

@@ -144,6 +144,127 @@ public class QueueServiceTests
         });
     }
 
+    // --- Arm: prerender-safe load without streaming (release embed) ---
+
+    [Test]
+    public void Arm_LoadsTracksAtIndexZero_WithoutStreaming()
+    {
+        var tracks = Tracks(3);
+
+        _queue.Arm(tracks);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(_queue.Items.Select(t => t.EntryKey),
+                Is.EqualTo(new[] { "track-1", "track-2", "track-3" }));
+            Assert.That(_queue.CurrentIndex, Is.EqualTo(0));
+            Assert.That(_queue.IsArmed, Is.True);
+            // Arming is interop-free state only: nothing must have been streamed yet.
+            Assert.That(_player.SelectedTracks, Is.Empty);
+        });
+    }
+
+    [Test]
+    public void Arm_WithSingleTrackRelease_ArmsAOneItemQueueWithoutError()
+    {
+        _queue.Arm(Tracks(1));
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(_queue.Items, Has.Count.EqualTo(1));
+            Assert.That(_queue.CurrentIndex, Is.EqualTo(0));
+            Assert.That(_queue.IsArmed, Is.True);
+            Assert.That(_queue.HasNext, Is.False);
+            Assert.That(_player.SelectedTracks, Is.Empty);
+        });
+    }
+
+    [Test]
+    public void Arm_WithEmptyTracks_IsNoOpAndLeavesQueueDisarmed()
+    {
+        _queue.Arm(Enumerable.Empty<TrackDto>());
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(_queue.Items, Is.Empty);
+            Assert.That(_queue.CurrentIndex, Is.EqualTo(-1));
+            Assert.That(_queue.IsArmed, Is.False);
+        });
+    }
+
+    [Test]
+    public async Task Start_OnArmedQueue_StreamsTrackZeroAndDisarms()
+    {
+        // Models the embed's first-gesture path: FramePlayer arms the queue (no stream), then the
+        // play click routes through Start().
+        _queue.Arm(Tracks(3));
+
+        await _queue.Start();
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(_queue.CurrentIndex, Is.EqualTo(0));
+            Assert.That(_queue.IsArmed, Is.False);
+            Assert.That(_player.SelectedTracks.Single().EntryKey, Is.EqualTo("track-1"));
+        });
+    }
+
+    [Test]
+    public async Task Start_OnUnarmedQueue_IsNoOp()
+    {
+        // A non-embed flow (PlayRelease already streaming) must not be disturbed by a stray Start.
+        await _queue.PlayRelease(Tracks(3));
+        var streamedBefore = _player.SelectedTracks.Count;
+
+        await _queue.Start();
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(_queue.IsArmed, Is.False);
+            Assert.That(_player.SelectedTracks, Has.Count.EqualTo(streamedBefore),
+                "Start on an unarmed queue must not re-stream");
+        });
+    }
+
+    [Test]
+    public async Task ArmedQueue_StartedThenAdvancesThroughWholeReleaseOnTrackEnded()
+    {
+        _queue.Arm(Tracks(3));
+        await _queue.Start();
+
+        _player.RaiseTrackEnded(); // → track-2
+        _player.RaiseTrackEnded(); // → track-3
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(_queue.CurrentIndex, Is.EqualTo(2));
+            Assert.That(_player.SelectedTracks.Select(t => t.EntryKey),
+                Is.EqualTo(new[] { "track-1", "track-2", "track-3" }));
+        });
+    }
+
+    [Test]
+    public void Arm_RaisesQueueChanged()
+    {
+        var raised = false;
+        _queue.QueueChanged += () => raised = true;
+
+        _queue.Arm(Tracks(2));
+
+        Assert.That(raised, Is.True);
+    }
+
+    [Test]
+    public async Task Clear_DisarmsAnArmedQueue()
+    {
+        _queue.Arm(Tracks(2));
+
+        _queue.Clear();
+
+        Assert.That(_queue.IsArmed, Is.False);
+        await Task.CompletedTask;
+    }
+
     // --- Next / Previous mechanics and bounds ---
 
     [Test]