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-RTPass.cppm

@@ -72,6 +72,11 @@ export namespace Crafter {
         // 0 means "no user bindings".
         const void*       handlesPtr   = nullptr;
         std::uint32_t     handlesCount = 0;
+        // Wavefront bounce budget: number of (TRACE; SHADE) iterations.
+        // 1 = primary rays only; 2 = primary + one continuation/shadow
+        // bounce; etc. The library unrolls GENERATE; (PREP; TRACE; SHADE)
+        // ×maxDepth; RESOLVE.
+        std::uint32_t     maxDepth     = 1;
 
         RTPass(PipelineRTWebGPU* p) : pipeline(p) {}
 
@@ -88,7 +93,8 @@ export namespace Crafter {
                 static_cast<std::int32_t>(gx),
                 static_cast<std::int32_t>(gy),
                 handlesPtr,
-                static_cast<std::int32_t>(handlesCount));
+                static_cast<std::int32_t>(handlesCount),
+                static_cast<std::int32_t>(maxDepth));
         }
     };
 }