docs: wavefront RT in README + design-doc status; add RTStress to examples

README.md

@@ -50,9 +50,16 @@ compute pipeline composed from user-supplied WGSL stages).
   bridge. Atlas (`r8unorm`, sub-region writes) is a separate path.
 - **PipelineRTVulkan / PipelineRTWebGPU / ShaderBindingTableVulkan /
   ShaderBindingTableWebGPU / RTPass** — ray-tracing pipelines. Vulkan
-  uses native RT pipelines + SBTs; WebGPU composes one compute
-  pipeline by stitching the traversal library, a generated hit-group
-  switch, and the user's raygen / closesthit / miss / anyhit WGSL.
+  uses native RT pipelines + SBTs; WebGPU compiles a **wavefront /
+  streaming** software tracer — five `@compute` kernels
+  (`GENERATE → PREP → TRACE → SHADE → RESOLVE`) sharing one module,
+  connected by GPU ray/hit/payload buffers and a GPU-driven indirect
+  bounce loop (`dispatchWorkgroupsIndirect`). TRACE carries zero user
+  code (traversal + intersection only); user raygen calls
+  `rtEmitPrimaryRay`, and closesthit / miss run in SHADE where they
+  `rtEmitRay` continuation/shadow rays and `rtAccumulate` radiance. An
+  optional Resolve shader tonemaps the linear accumulator. See
+  [WAVEFRONT-DESIGN.md](WAVEFRONT-DESIGN.md).
 - **ComputeShader / WebGPUComputeShader** — Tier 1 wrapper used by the
   UI system. Vulkan loads a `.spv` and dispatches with
   `vkCmdPushDataEXT`; WebGPU loads a user-supplied `.wgsl` blob at
@@ -145,6 +152,10 @@ See [examples/](examples/). Quick map:
 - [VulkanTriangle](examples/VulkanTriangle/) — ray-traced triangle on
   both Vulkan and WebGPU. The smallest test of the bindless + RT path
   on each backend.
+- [RTStress](examples/RTStress/) — wavefront RT benchmark: an N×N×N grid
+  of a cube mesh (instance-count knob `kGrid`, 512 → 8000) shaded with
+  primary + shadow rays. Prints a GPU timestamp-query per-pass breakdown
+  each second. WebGPU/DOM only.
 - [Sponza](examples/Sponza/) — ray-traced Sponza atrium on both
   backends. Exercises `.cmesh` / `.ctex` decompression (GPU
   `VK_EXT_memory_decompression` on Vulkan, CPU on WebGPU) and a