refactor(animation): extract live PartArray presenter

Move final live part composition, exact-incarnation schedule handoff, MotionDone binding, and presentation diagnostics out of GameWindow while preserving the retail frame order. Reject stale schedule and completion ABA at the new owner boundary.

Co-Authored-By: OpenAI Codex <codex@openai.com>

src/AcDream.App/Rendering/LiveEntityAnimationState.cs

@@ -0,0 +1,63 @@
+using System.Numerics;
+using AcDream.App.World;
+using AcDream.Core.Physics;
+using AcDream.Core.Physics.Motion;
+using AcDream.Core.World;
+using DatReaderWriter.DBObjs;
+using DatReaderWriter.Types;
+
+namespace AcDream.App.Rendering;
+
+/// <summary>
+/// Incarnation-owned live <c>CPartArray</c> presentation state. Time, root
+/// motion, and hooks remain owned by <see cref="LiveEntityAnimationScheduler"/>;
+/// this component retains the final part-presentation channels only.
+/// </summary>
+internal sealed class LiveEntityAnimationState : ILiveEntityAnimationRuntime
+{
+    public required WorldEntity Entity;
+    WorldEntity ILiveEntityAnimationRuntime.Entity => Entity;
+    uint ILiveEntityAnimationRuntime.CurrentMotion => Sequencer?.CurrentMotion ?? 0u;
+
+    public required Setup Setup;
+    public required Animation Animation;
+    public required int LowFrame;
+    public required int HighFrame;
+    public required float Framerate;
+    public required float Scale;
+    public required IReadOnlyList<LiveAnimationPartTemplate> PartTemplate;
+    public required IReadOnlyList<bool> PartAvailability;
+    public float CurrFrame;
+    public AnimationSequencer? Sequencer;
+
+    public IReadOnlyList<PartTransform>? PreparedSequenceFrames;
+    public bool SequenceAdvancedBeforeAnimationPass;
+    public readonly Frame RootMotionScratch = new();
+    public readonly MotionDeltaFrame RootMotionDeltaScratch = new();
+
+    /// <summary>Reusable compact drawable channel, consumed before draw.</summary>
+    public readonly List<MeshRef> MeshRefsScratch = new();
+    /// <summary>Reusable indexed rigid/effect channel.</summary>
+    public readonly List<Matrix4x4> EffectPartPosesScratch = new();
+    /// <summary>
+    /// Indexed visible transforms retained separately from the rigid channel
+    /// because Setup DefaultScale affects geometry but not attachments.
+    /// </summary>
+    public readonly List<Matrix4x4> VisualPartPosesScratch = new();
+    public bool PresentationPosesInitialized;
+
+    public double LastSequenceDiagnosticTime;
+    public double LastPartDiagnosticTime;
+
+    public void InvalidatePresentationPoses()
+    {
+        PresentationPosesInitialized = false;
+        VisualPartPosesScratch.Clear();
+        EffectPartPosesScratch.Clear();
+    }
+}
+
+internal readonly record struct LiveAnimationPartTemplate(
+    uint GfxObjId,
+    IReadOnlyDictionary<uint, uint>? SurfaceOverrides,
+    bool IsDrawable);