Adds the native counterpart of the WebGPU Mesh::BuildProcedural: uploads
the boxes as a 24-byte-stride VkAabbPositionsKHR-compatible device buffer
(AS-build-input read-only + device address) and builds the BLAS from one
VK_GEOMETRY_TYPE_AABBS_KHR geometry. opaque maps to
VK_GEOMETRY_OPAQUE_BIT_KHR, default-false semantics matching the WebGPU
path so any-hit shaders run. The BLAS sizing/create/build tail is factored
into a geometry-type-agnostic helper shared with the triangle path; no
TLAS/instance changes needed.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
