Node material 5 terminates Playground on ANGLE over the Basic Render Driver

[Filed by Copilot on behalf of @bghgary]

`Node material 5` ([playground `#V8VH7B#0`](https://playground.babylonjs.com/#V8VH7B#0)) terminates Playground when ANGLE uses the Direct3D Basic Render Driver. It reproduced twice at the same point on a GitHub Windows runner, exiting with `0xC0000409` and no assertion text.

| Configuration | Renderer | Result |
|---|---|---|
| Ubuntu OpenGL | llvmpipe | validated |
| Windows OpenGL, discrete GPU | ANGLE on RTX 4080 | validated |
| Windows OpenGL, GitHub runner | ANGLE on Basic Render Driver | **process terminated** |

Software rendering alone is not sufficient to reproduce it because llvmpipe passes.

## Possible lead

The last output is ANGLE's translated HLSL for a vertex shader sampling a texture with `SampleLevel`. Vertex texture fetch is a lead, not a confirmed cause.

## Follow-up

[#1812](https://github.com/BabylonJS/BabylonNative/pull/1812) initially added Windows OpenGL CI and exposed this failure. That PR was reduced to the local Windows OpenGL build fix; CI is deferred until this issue is fixed.

Reproduction needs Windows without a hardware graphics adapter; `ANGLE_PREFERRED_DEVICE` did not redirect ANGLE to WARP locally. Crash dumps from the original CI attempt are attached to [this run](https://github.com/BabylonJS/BabylonNative/actions/runs/30868718426).