feat(install): #59 NVIDIA commented system.nix guidance

When hardwareProfile includes common-gpu-nvidia, emit a comment-only
plain NixOS block (PRIME / powerManagement / open-module) in the
installer region of system.nix — same pattern as ROCm/NPU opt-ins.
HARDWARE.md §6 product direction marked shipped. Close #59.

Verified: V0 (patch-template smoke + negative + bash -n).

pkgs/nomarchy-install/patch-template.py

@@ -117,7 +117,10 @@ def build_installer_region(v: dict) -> str:
             )
 
     hw = v.get("hardware") or {}
-    if any(hw.get(k) for k in ("intel", "amd", "fingerprint", "cameraIr", "npu")):
+    if any(
+        hw.get(k)
+        for k in ("intel", "amd", "fingerprint", "cameraIr", "npu", "nvidia")
+    ):
         lines.append("  # Hardware enablement (auto-detected).")
     if hw.get("intel"):
         lines.append(
@@ -151,6 +154,17 @@ def build_installer_region(v: dict) -> str:
             f"  # nomarchy.hardware.npu.enable = true;            # {vendor} NPU (experimental; userspace BYO)",
             "  # nomarchy.hardware.latestKernel = true;          # if the NPU driver needs a newer kernel",
         ]
+    # NVIDIA: profile is in flake.nix (common-gpu-nvidia). Hybrid/PRIME
+    # knobs are plain NixOS — comment-only guidance, same pattern as ROCm.
+    if hw.get("nvidia"):
+        lines += [
+            "  # NVIDIA: common-gpu-nvidia is in hardwareProfile (flake.nix).",
+            "  # Hybrid/PRIME, power, open-module — plain NixOS; see docs/HARDWARE.md §6",
+            "  # and https://wiki.nixos.org/wiki/Nvidia (bus IDs are machine-specific).",
+            "  # hardware.nvidia.prime = { ... };                 # offload/sync",
+            "  # hardware.nvidia.powerManagement.enable = true;   # suspend/resume",
+            "  # hardware.nvidia.open = false;                    # true = open module (newer cards)",
+        ]
 
     if v.get("resumeOffset") is not None:
         root_uuid = nix_str(v["rootUuid"])