feat: 新增 laptop 主机配置（Ultra 9 285H / Arc）

- hosts/laptop/hardware.nix: 本机真实硬件配置（btrfs 子卷 / NPU / 微码）
- hosts/laptop/default.nix: 复用 common/desktop-plasma/chinese/gaming/printing/apps，跳过 nvidia 与 fpga；加 Intel Arc VA-API
- flake.nix: 抽出 mkSystem，新增 nixosConfigurations.laptop / nixos

flake.nix

@@ -1,5 +1,5 @@
 {
-  description = "whc NixOS — desktop (i7-12700F + RTX 4060)";
+  description = "whc NixOS — desktop (i7-12700F + RTX 4060) + laptop (Ultra 9 285H / Arc)";
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
@@ -9,11 +9,17 @@
     { self, nixpkgs, ... }:
     let
       system = "x86_64-linux";
+      mkSystem = host: nixpkgs.lib.nixosSystem {
+        inherit system;
+        modules = [ (./hosts + "/${host}") ];
+      };
     in
     {
-      nixosConfigurations.desktop = nixpkgs.lib.nixosSystem {
-        inherit system;
-        modules = [ ./hosts/desktop ];
+      nixosConfigurations = {
+        desktop = mkSystem "desktop";
+        laptop = mkSystem "laptop";
+        # hostname 仍是 nixos：让不带 attr 的 `nixos-rebuild --flake .#` 也能命中
+        nixos = mkSystem "laptop";
       };
 
       # 无 flake 时也可：把本仓库拷到 /etc/nixos 后 nixos-rebuild switch

hosts/laptop/default.nix

@@ -0,0 +1,26 @@
+# 笔记本：Intel Core Ultra 9 285H + Intel Arc（Arrow Lake-P），无 NVIDIA
+{ pkgs, ... }:
+
+{
+  imports = [
+    ./hardware.nix
+    ../../modules/common.nix
+    ../../modules/desktop-plasma.nix
+    ../../modules/chinese.nix
+    ../../modules/gaming.nix
+    ../../modules/printing.nix
+    ../../modules/apps.nix
+    # 本机无 NVIDIA：刻意不导入 ../../modules/nvidia.nix
+    # FPGA 工具链依赖 Qt5，在 unstable 上求值风险高，暂不导入 ../../modules/fpga.nix
+  ];
+
+  networking.hostName = "nixos";
+
+  # 笔记本不照抄 desktop 的 "performance"，交给内核默认调度
+  # powerManagement.cpuFreqGovernor = "powersave";
+
+  # Intel Arc 硬解（VA-API），可选
+  hardware.graphics.extraPackages = [ pkgs.intel-media-driver ];
+
+  system.stateVersion = "26.05";
+}

hosts/laptop/hardware.nix

@@ -0,0 +1,46 @@
+# Do not modify this file!  It was generated by ‘nixos-generate-config’
+# and may be overwritten by future invocations.  Please make changes
+# to /etc/nixos/configuration.nix instead.
+{ config, lib, pkgs, modulesPath, ... }:
+
+{
+  imports =
+    [ (modulesPath + "/installer/scan/not-detected.nix")
+    ];
+
+  boot.initrd.availableKernelModules = [ "xhci_pci" "thunderbolt" "nvme" "uas" "sd_mod" ];
+  boot.initrd.kernelModules = [ ];
+  boot.kernelModules = [ "kvm-intel" ];
+  boot.extraModulePackages = [ ];
+
+  fileSystems."/" =
+    { device = "/dev/disk/by-uuid/cbcb5930-50a9-4ff8-92f9-4622bd869579";
+      fsType = "btrfs";
+    };
+
+  fileSystems."/home" =
+    { device = "/dev/disk/by-uuid/cbcb5930-50a9-4ff8-92f9-4622bd869579";
+      fsType = "btrfs";
+      options = [ "subvol=home" ];
+    };
+
+  fileSystems."/nix" =
+    { device = "/dev/disk/by-uuid/cbcb5930-50a9-4ff8-92f9-4622bd869579";
+      fsType = "btrfs";
+      options = [ "subvol=nix" ];
+    };
+
+  fileSystems."/boot" =
+    { device = "/dev/disk/by-uuid/84D8-EB50";
+      fsType = "vfat";
+      options = [ "fmask=0077" "dmask=0077" ];
+    };
+
+  swapDevices =
+    [ { device = "/dev/disk/by-uuid/d62e342b-271a-40e7-912d-3a748b5f55a1"; }
+    ];
+
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
+  hardware.cpu.intel.npu.enable = true;
+  hardware.cpu.intel.updateMicrocode = lib.mkDefault config.hardware.enableRedistributableFirmware;
+}