feat(ufbx): switch to native ufbx_vec/quat/matrix types

Replaces all Misaki.HighPerformance.Mathematics vector, quaternion, and matrix types in Ghost.Ufbx bindings with new native ufbx_vec2, ufbx_vec3, ufbx_vec4, ufbx_quat, and ufbx_matrix structs. Updates all interop code, struct fields, and API signatures accordingly. Adds struct definitions for the new types and provides matrix operations as struct methods. Removes unnecessary math package reference. Also includes minor fixes to system attributes, meshlet LOD logic, and mesh utility.

BREAKING CHANGE: All Ufbx-related APIs now use ufbx_* types instead of Misaki.HighPerformance.Mathematics types. Existing code using the old types will require updates.

src/ThridParty/Ghost.Ufbx/Generated/ufbx_matrix.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
@@ -118,7 +119,7 @@ namespace Ghost.Ufbx
         }
 
         [UnscopedRef]
-        public Span<System.Numerics.Vector3> cols
+        public Span<ufbx_vec3> cols
         {
             get
             {
@@ -192,7 +193,7 @@ namespace Ghost.Ufbx
             [InlineArray(4)]
             public partial struct _cols_e__FixedBuffer
             {
-                public System.Numerics.Vector3 e0;
+                public ufbx_vec3 e0;
             }
 
             [InlineArray(12)]