feat(vfx): bind effects to live animated poses

src/AcDream.Core/World/WorldEntity.cs

@@ -30,6 +30,30 @@ public sealed class WorldEntity
     /// </summary>
     public required IReadOnlyList<MeshRef> MeshRefs { get; set; }
 
+    /// <summary>
+    /// Stable Setup-part-indexed poses used by attachment and effect hooks.
+    /// Unlike <see cref="MeshRefs"/>, this array never compacts around a DAT
+    /// part whose GfxObj could not be loaded. <see cref="IndexedPartAvailable"/>
+    /// distinguishes a real indexed part from a retained placeholder pose.
+    /// </summary>
+    public IReadOnlyList<Matrix4x4> IndexedPartTransforms { get; private set; } =
+        Array.Empty<Matrix4x4>();
+
+    public IReadOnlyList<bool> IndexedPartAvailable { get; private set; } =
+        Array.Empty<bool>();
+
+    public void SetIndexedPartPoses(
+        IReadOnlyList<Matrix4x4> transforms,
+        IReadOnlyList<bool> available)
+    {
+        ArgumentNullException.ThrowIfNull(transforms);
+        ArgumentNullException.ThrowIfNull(available);
+        if (transforms.Count != available.Count)
+            throw new ArgumentException("Indexed part pose and availability counts must match.");
+        IndexedPartTransforms = transforms;
+        IndexedPartAvailable = available;
+    }
+
     /// <summary>
     /// Optional per-entity palette override (server-specified base +
     /// subpalette overlays). When non-null, applies to every palette-