On Windows wgpu enumerates each physical GPU once per backend (Vulkan +
DX12) plus a CPU-emulated fallback ("Microsoft Basic Render Driver").
Building a mining context for every entry causes VRAM contention and
OOMs the process during benchmark/serve startup (#61).
Instead of deduplicating by (vendor, device) PCI IDs - which would
collapse rigs with multiple identical cards into a single context - drop
CPU-emulated adapters and keep all adapters from the highest-ranked
backend present (Vulkan/Metal, then DX12). Within a single backend each
physical GPU appears exactly once, so identical cards are preserved by
construction and no physical-ID matching is needed.
Selected adapters are ordered discrete-first so `--gpu-devices 1` picks
the discrete card on hybrid laptops. Skipped adapters are logged at info
level; if nothing usable remains, init fails with an explicit error.
Selection logic is a pure index-based function unit-tested against the
exact enumeration reported in #61, identical multi-GPU rigs, DX12-only
machines, and software-only environments.
Co-authored-by: illuzen <illuzen@users.noreply.github.com>
