feat(hardware): nomarchy.hardware.* enablement beyond nixos-hardware

The nixos-hardware "common-*" profiles the installer selects cover the
basics (microcode, the Intel/AMD VA-API media stack, weekly fstrim), and
power.nix adds thermald + power-profiles-daemon. This adds the gap above
them, generically and detected at install time.

New modules/nixos/hardware.nix exposes a vendor-keyed nomarchy.hardware.*
surface — broadly-beneficial bits default ON when the vendor is detected
(opt-out), heavy/experimental bits behind opt-in toggles:
  - intel.enable -> GuC/HuC (i915.enable_guc=3); intel.computeRuntime
    (opt-in: intel-compute-runtime + vpl-gpu-rt)
  - amd.enable -> amd_pstate=active + radeonsi VA-API env; amd.rocm.enable
    + amd.rocm.gfxOverride (opt-in: ROCm HIP/OpenCL)
  - fingerprint.enable -> fprintd; fingerprint.pam (opt-in: login + sudo)
  - npu.enable (opt-in/experimental) -> the in-kernel driver
    (amdxdna/intel_vpu) keyed by vendor; userspace runtime is BYO

hardware-db.sh now detects Intel/AMD, a fingerprint reader (libfprint USB
vendor IDs) and an NPU (Intel VPU / AMD XDNA PCI IDs), emitting NOMARCHY
lines the installer bakes into system.nix — safe defaults active, opt-ins
commented. Audited against the commons to avoid double-setting.

Verified: flake check green; a toggles-on build has amd_pstate=active +
i915.enable_guc=3 in kernel-params and ships fprintd.service; detection
runs correctly on the (AMD Ryzen-AI) dev machine. On-hardware verification
of the AMD/NPU/Intel-compute runtime bits is still pending.

Docs: template commented examples, README option table, ROADMAP status.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

templates/downstream/system.nix

@@ -31,6 +31,17 @@
   #   thermal.enable = true;                   #   thermald (Intel CPUs)
   # };
   #
+  # nomarchy.hardware = {                       # enablement above nixos-hardware (installer-detected)
+  #   intel.enable = true;                      #   GuC/HuC firmware; installer sets this on Intel
+  #   intel.computeRuntime = true;              #   OpenCL/oneVPL GPU compute (opt-in)
+  #   amd.enable = true;                        #   amd-pstate + radeonsi VA-API; installer-set on AMD
+  #   amd.rocm.enable = true;                   #   ROCm GPU compute (multi-GB, opt-in)
+  #   amd.rocm.gfxOverride = "11.0.0";          #   HSA override for an unlisted iGPU
+  #   fingerprint.enable = true;                #   fprintd; installer-set when a reader is detected
+  #   fingerprint.pam = true;                   #   use the fingerprint for login + sudo
+  #   npu.enable = true;                        #   on-die NPU driver (experimental; userspace runtime BYO)
+  # };
+  #
   # nomarchy.services.tailscale.enable = true; # mesh VPN — then `sudo tailscale up`
   # nomarchy.services.syncthing.enable = true; # file sync — GUI at http://127.0.0.1:8384
   # nomarchy.services.podman.enable = true;    # rootless containers (docker → podman)