PipelineRTWebGPU emits a runIntersection mega-switch and the
RT_HAS_ANYHIT / RT_HAS_INTERSECTION consts (+ the @CRAFTER_RT_TRACE_USER
marker) that gate the library's new TRACE-stage user callbacks, so an
opaque triangle-only scene still const-folds them away. Mesh-WebGPU
builds a SAH BVH2 over AABB primitives and uploads them in primitive
order for the intersection shader to fetch.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
