Metal shaders were not cooked

A warning from the shader cook: Apple's Metal Shader Converter was not found, so the cooked pipelines got SPIR-V and DXIL but no metallib artifacts. The cook still succeeds and Windows/Linux are unaffected. The macOS Metal backend refuses those pipelines with ARA_GPU_CONTRACT ("no Metal artifacts").

#Common causes

• The converter is not installed on this cook host (it is a free, signed-in download from Apple and an optional setup step).
• ARA_METAL_SHADERCONVERTER is set to off or to an empty value.
• It is installed somewhere other than PATH or Apple's default location.

#Fixes

• On the canonical cook host (Windows), install Metal Shader Converter for Windows from https://developer.apple.com/download/all/?q=metal%20shader%20converter, then recook.

• Point ARA_METAL_SHADERCONVERTER at metal-shaderconverter if it lives elsewhere.

• Never commit cooked artifacts produced on a Mac; recook on the canonical host instead (docs/dev/macos.md).

• Code: ARA_GPU_METAL_COOK_SKIPPED (slot 6007)

• Constant: GPU_METAL_COOK_SKIPPED

• Reported by: ara-shader-cook