feat(rendering): pack scene dispatcher inputs

Capture immutable presentation payloads in the render scene, flatten unique entity and mesh-part records into the borrowed frame arena, and compare every routed dispatcher input tuple without changing the production draw source.

src/AcDream.App/Rendering/Scene/RenderSceneContracts.cs

@@ -1,4 +1,5 @@
 using System.Numerics;
+using AcDream.Core.World;
 
 namespace AcDream.App.Rendering.Scene;
 
@@ -194,6 +195,18 @@ internal readonly record struct RenderSourceMetadata(
     RenderSceneHash128 AppearanceFingerprint,
     uint CurrentProjectionFlags = 0);
 
+/// <summary>
+/// Borrowed immutable presentation payload captured at a scene publication
+/// edge. WorldEntity replaces its MeshRefs collection when animated or
+/// appearance state changes, so retaining this exact collection reference is
+/// a snapshot rather than a callback into gameplay state. G2 copies it into
+/// the reusable frame arena before any dispatcher consumer observes it.
+/// </summary>
+internal readonly record struct RenderEntityPayload(
+    IReadOnlyList<MeshRef> MeshRefs,
+    PaletteOverride? PaletteOverride,
+    bool IsBuildingShell);
+
 internal readonly record struct RenderProjectionRecord(
     RenderProjectionId Id,
     RenderProjectionClass ProjectionClass,
@@ -208,7 +221,8 @@ internal readonly record struct RenderProjectionRecord(
     RenderDegradeState DegradeState,
     RenderSortKey SortKey,
     RenderDirtyMask DirtyMask,
-    RenderSourceMetadata Source = default);
+    RenderSourceMetadata Source = default,
+    RenderEntityPayload EntityPayload = default);
 
 internal enum RenderProjectionDeltaKind : byte
 {