WebGPU RT: wavefront tracer core (GENERATE/PREP/TRACE/SHADE/RESOLVE)

Replace the megakernel @compute entry with five wavefront kernels sharing
one module, connected by GPU ray/hit/payload buffers and a GPU-driven
indirect bounce loop:

  GENERATE -> (PREP -> TRACE -> SHADE) x maxDepth -> RESOLVE

- TRACE contains zero user code (pure _rtwTraverseTlas/Blas, opaque-only).
- PREP publishes dispatchWorkgroupsIndirect args from the live ray count;
  the indirect-args buffer lives in its own bind group so it is never
  bound read-write in the same dispatch that consumes it as INDIRECT.
- New emit/accumulate API: rtEmitPrimaryRay / rtEmitRay / rtAccumulate,
  plus an optional user Resolve stage (tonemap hook; identity by default).
- Per-pass WfParams via a dynamic-offset uniform ring (curIsA/bounce vary
  between passes within one submit).
- Payload-typed wfPayload binding emitted in the codegen region after the
  user's struct Payload; payload travels with each ray (2*W*H slots).
- Request maxBufferSize / maxStorageBufferBindingSize / maxComputeWorkgroups
  PerDimension so the W*H-sized work buffers fit past the 128MB baseline.

VulkanTriangle ported to the new API and renders bit-identical to the
megakernel baseline at maxDepth=1.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

interfaces/Crafter.Graphics-WebGPU.cppm

@@ -201,7 +201,8 @@ namespace Crafter::WebGPU {
                                    std::uint32_t tlasBufHandle,
                                    std::int32_t  instanceCount,
                                    std::int32_t  gx, std::int32_t gy,
-                                   const void* handlesPtr, std::int32_t handlesCount);
+                                   const void* handlesPtr, std::int32_t handlesCount,
+                                   std::int32_t maxDepth);
 
     // GPU TLAS-build dispatch. Two sequential compute passes:
     //   1. tlasBuildMain — per-instance world AABB + identity permutation