Restructure Sponza for the wavefront model: raygen emits the primary ray;
closesthit (in SHADE) gathers albedo/normal, accumulates ambient, and
emits a shadow ray carrying the pending direct term; miss adds the sky
(primary) or the direct term (shadow miss). resolve.wgsl applies the same
Reinhard+gamma the megakernel raygen did inline. User bindings moved to
group 3 (groups 0..2 reserved). RTPass maxDepth=2.
Renders the atrium correctly through the wavefront pipeline (textures,
two-sided shading, sun+ambient, shadows, tonemap).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
