These are already covered by nixpkgs defaults in kernel.nix
(nvme, xhci_pci, usbhid, sd_mod) or detected by
nixos-generate-config via PCI/USB class scanning
(thunderbolt, usb_storage).
Add hardware support for:
- UM690 (AMD Ryzen 9 6900HX, Radeon 680M)
- UM690S (slim variant)
- UM790 Pro (AMD Ryzen 9 7940HS, Radeon 780M)
These share a common um-series.nix module for consistent configuration
across the UM series AMD-based mini PCs.
