Single translation unit that compiles the V-HACD implementation.

V-HACD is a header-only library (VHACD.h). Its header gates the actual algorithm behind the ENABLE_VHACD_IMPLEMENTATION macro — exactly like stb_image and dr_libs style single-headers. The implementation is compiled only when GROUP2_ENABLE_VHACD is explicitly enabled. Production map collision is authored as static triangle meshes and does not use this path.