wgpu's default DX12 compiler (Auto) loads whichever dxcompiler.dll the DLL
search path finds first. LightCraft ships none, so it picked up another
program's copy; one without dxil.dll beside it (e.g. DXC 1.7) warns that
the DXIL is unsigned, wgpu treats that as a compile error, its
indirect-validation pipelines fail, the device is lost and the window
never opens ("Parent device is lost", exit code 1).
Every wgpu instance (window and both compute devices) now uses
lightcraft_gpu::backend::backend_options(): wgpu's env options with the
DX12 compiler pinned to FXC (d3dcompiler_47.dll, part of Windows), unless
WGPU_DX12_COMPILER asks for another.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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