feat(systems): add tortoise NixOS host configuration

Registers the tortoise machine in flake.nix and adds its system
configuration with a placeholder hardware config (ZFS root pool,
x86_64) to be replaced by the installer-generated hardware-configuration.nix.

flake.nix

@@ -126,6 +126,12 @@
           ];
           specialArgs = { inherit inputs outputs; };
         };
+        tortoise = lib.nixosSystem {
+          modules = [
+            ./systems/tortoise
+          ];
+          specialArgs = { inherit inputs outputs; };
+        };
         iso = lib.nixosSystem {
           modules = [
             ./systems/iso

systems/tortoise/default.nix

@@ -0,0 +1,37 @@
+{ inputs, ... }:
+{
+  imports = [
+    "${inputs.self}/users/richie"
+    "${inputs.self}/common/global"
+    "${inputs.self}/common/optional/monitoring-agent.nix"
+    "${inputs.self}/common/optional/ssh_decrypt.nix"
+    "${inputs.self}/common/optional/systemd-boot.nix"
+    "${inputs.self}/common/optional/update.nix"
+    "${inputs.self}/common/optional/zerotier.nix"
+    ./hardware.nix
+  ];
+
+  boot.kernelParams = [ "panic=10" ];
+
+  networking = {
+    hostName = "tortoise";
+    hostId = "161cbd68";
+    firewall.enable = true;
+    networkmanager.enable = true;
+  };
+
+  services = {
+    openssh.ports = [ 867 ];
+  };
+
+  systemd = {
+    enableEmergencyMode = false;
+    # Only takes effect if the board exposes a hardware watchdog device.
+    settings.Manager = {
+      RuntimeWatchdogSec = "30s";
+      RebootWatchdogSec = "2m";
+    };
+  };
+
+  system.stateVersion = "26.11";
+}

systems/tortoise/hardware.nix

@@ -0,0 +1,69 @@
+{
+  config,
+  lib,
+  modulesPath,
+  ...
+}:
+{
+  imports = [ (modulesPath + "/installer/scan/not-detected.nix") ];
+
+  boot = {
+    initrd = {
+      availableKernelModules = [
+        "ahci"
+        "ehci_pci"
+        "nvme"
+        "sd_mod"
+        "usb_storage"
+        "usbhid"
+        "xhci_pci"
+      ];
+      kernelModules = [ ];
+      luks.devices."luks-root-pool-ata-Samsung_SSD_870_EVO_4TB_S757NL0Y315721H-part2" = {
+        device = "/dev/disk/by-id/ata-Samsung_SSD_870_EVO_4TB_S757NL0Y315721H-part2";
+        bypassWorkqueues = true;
+        allowDiscards = true;
+      };
+    };
+    kernelModules = [ "kvm-intel" ];
+    extraModulePackages = [ ];
+  };
+
+  fileSystems = {
+    "/" = lib.mkDefault {
+      device = "root_pool/root";
+      fsType = "zfs";
+    };
+
+    "/home" = {
+      device = "root_pool/home";
+      fsType = "zfs";
+    };
+
+    "/var" = {
+      device = "root_pool/var";
+      fsType = "zfs";
+    };
+
+    "/nix" = {
+      device = "root_pool/nix";
+      fsType = "zfs";
+    };
+
+    "/boot" = {
+      device = "/dev/disk/by-uuid/223B-9F08";
+      fsType = "vfat";
+      options = [
+        "fmask=0077"
+        "dmask=0077"
+      ];
+    };
+  };
+
+  swapDevices = [ ];
+
+  networking.useDHCP = lib.mkDefault true;
+
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
+  hardware.cpu.intel.updateMicrocode = lib.mkDefault config.hardware.enableRedistributableFirmware;
+}

users/richie/systems/tortoise.nix

@@ -0,0 +1,5 @@
+{
+  imports = [
+    ../home/global.nix
+  ];
+}