fix(animation): harden presentation phase handoffs

Own every borrowed PartArray frame across callbacks, version presentation state across appearance rebinding, reject recursive phase consumption, and preserve static MotionDone when only a stale visual pose is discarded.

src/AcDream.Core/Physics/AnimationSequencer.cs

@@ -248,10 +248,9 @@ public sealed class AnimationSequencer
     // allocation instead of one `new PartTransform[partCount]` per Advance()
     // call (every animated entity, every tick, including idle NPCs on a
     // breathe cycle). BuildBlendedFrame/BuildIdentityFrame overwrite every
-    // slot before returning this array, so the values are bit-identical to
-    // the old fresh-array version; callers (GameWindow.TickAnimations)
-    // consume the returned IReadOnlyList<PartTransform> synchronously within
-    // the same loop iteration and never cache it across Advance() calls.
+    // authored slot before returning this view. The view is borrowed only for
+    // the producing call: App schedulers copy its authored prefix into their
+    // incarnation-owned handoff buffer before any callback or later phase.
     private readonly PartTransform[] _partTransformScratch;
     private readonly PartTransformBuffer _partTransformView;