docs(vulkan-rt): record native descriptor-heap AS read as a driver fault

Investigated the VK_ERROR_DEVICE_LOST on the native VulkanTriangle (#7).
Verified the engine side is correct and validation-clean: the BLAS/TLAS
build finishes before render (FinishInit waits), the built instance is
well-formed (identity transform, mask=0xFF, correct BLAS ref), and
vkWriteResourceDescriptorsEXT stores the TLAS device address at the
expected heap offset (confirmed by dumping the heap bytes). Khronos
validation 1.4.350 reports zero errors.

The fault is isolated to reading the acceleration structure through
VK_EXT_descriptor_heap:
- images/buffers via the same heap render fine (trace disabled -> the
  raygen imageStore path renders a full gradient);
- both traceRayEXT and inline rayQueryEXT (no SBT) fault identically on
  the AS read;
- reproduces with the AS descriptor at heap byte 0 / shader index 0 (no
  offset/stride ambiguity) and regardless of pAddressRange size.

NVIDIA 610.43.02 is the only descriptor_heap implementation available
(llvmpipe lacks the extension), so there is no second implementation to
cross-check. Conclusion: driver-side fault in NVIDIA's brand-new
VK_EXT_descriptor_heap acceleration-structure path; should be reported to
NVIDIA. The traceRayEXT call is left active so the example stays a
faithful reproducer. Documented in both READMEs.

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

README.md

@@ -24,6 +24,15 @@ Vulkan ray tracing is hardware (`VK_KHR_ray_tracing_pipeline`); WebGPU
 ray tracing is a library-built software path (BVH + traceRay in a
 compute pipeline composed from user-supplied WGSL stages).
 
+> **Native RT status:** reading an acceleration structure through
+> `VK_EXT_descriptor_heap` currently aborts with `VK_ERROR_DEVICE_LOST` on
+> NVIDIA driver `610.43.02` — a driver-side fault in the brand-new
+> descriptor-heap acceleration-structure path, not an engine bug. The
+> engine setup (build, descriptors, SBT) is correct and validation-clean,
+> and images/buffers through the same heap work. See
+> [examples/VulkanTriangle/README.md](examples/VulkanTriangle/README.md)
+> for the full investigation. WebGPU RT is unaffected.
+
 ## What's in here
 
 - **Window** — Wayland, Win32, and DOM backends, swapchain ring / canvas