feat: add BufferGeometryUtils for advanced geometry manipulation

- Implemented computeMikkTSpaceTangents for consistent tangent generation.
- Added mergeGeometries to combine multiple BufferGeometries.
- Introduced mergeAttributes for merging BufferAttributes.
- Created deepCloneAttribute for cloning BufferAttributes.
- Developed interleaveAttributes and deinterleaveAttribute for attribute management.
- Added estimateBytesUsed to calculate memory usage of geometries.
- Implemented mergeVertices to optimize vertex data.
- Created toTrianglesDrawMode for converting geometries to triangle mode.
- Added computeMorphedAttributes for handling morph targets in geometries.
- Implemented mergeGroups to consolidate geometry groups.
- Developed toCreasedNormals for generating smooth normals with crease angles.

klabava/THIRD_PARTY.txt

@@ -1,4 +1,6 @@
-Three.js r180 / 0.180.0 is loaded from jsDelivr. It is not bundled here.
+Three.js r180 / 0.180.0 is bundled in vendor/three/.
+The MIT license is included at vendor/three/LICENSE.
+Source files were obtained from the version-pinned official npm distribution on jsDelivr.
 Source: https://github.com/mrdoob/three.js/tree/r180
 License: MIT, Copyright (c) 2010-2025 three.js authors.