fix: complete retail parity stability pass

tests/AcDream.App.Tests/Rendering/LiveEntityAnimationPresenterTests.cs

@@ -381,6 +381,50 @@ public sealed class LiveEntityAnimationPresenterTests
         Assert.Equal(0.5f, fixture.State.CurrFrame);
     }
 
+    [Fact]
+    public void LegacyCycle_WrapsAndInterpolatesThroughSharedRetailPlayback()
+    {
+        var fixture = Build(partCount: 1);
+        fixture.State.Sequencer = null;
+        fixture.State.LowFrame = 0;
+        fixture.State.HighFrame = 2;
+        fixture.State.Framerate = 2f;
+        fixture.State.CurrFrame = 2.5f;
+        var animation = new Animation();
+        foreach (float x in new[] { 0f, 10f, 20f })
+        {
+            var frame = new AnimationFrame(1);
+            frame.Frames.Add(new Frame
+            {
+                Origin = new Vector3(x, 0f, 0f),
+                Orientation = Quaternion.Identity,
+            });
+            animation.PartFrames.Add(frame);
+        }
+        fixture.State.Animation = animation;
+        var schedule = new LiveEntityAnimationSchedule(
+            SequenceFrames: null,
+            LegacyAdvanceSeconds: 0.5f,
+            ComposeParts: true,
+            fixture.Record,
+            fixture.Entity,
+            fixture.State,
+            fixture.Record.ObjectClockEpoch,
+            fixture.Record.ProjectionMutationVersion,
+            fixture.State.PresentationRevision);
+        var presenter = Presenter(fixture.Live, new EntityEffectPoseRegistry(), new Context());
+
+        presenter.Present(new Dictionary<RuntimeEntityKey, LiveEntityAnimationSchedule>
+        {
+            [fixture.Record.ProjectionKey!.Value] = schedule,
+        });
+
+        // Legacy arithmetic: 2.5 + (0.5 * 2) = 3.5, wrapped over the
+        // inclusive 0..2 span to 0.5, then interpolated halfway 0 -> 10.
+        Assert.Equal(0.5f, fixture.State.CurrFrame);
+        Assert.Equal(new Vector3(5f, 0f, 0f), fixture.Entity.MeshRefs[0].PartTransform.Translation);
+    }
+
     private static LiveEntityAnimationPresenter Presenter(
         LiveEntityRuntime live,
         EntityEffectPoseRegistry poses,