Function recommend_inference_backend 

pub fn recommend_inference_backend(caps: &GpuAdapterCaps) -> &'static str

Capability-aware recommendation for which GPU backend this machine should run inference on (advisory; surfaced by the doctor/setup checker). Prefers the portable, vendor-neutral path so the build is not silently locked to Windows (DX12) or NVIDIA (CUDA). Reactive to the adapter actually in hand; a full enumerate-all-backends-and-pick is the next layer.