feat: add openclaw node service and migrate to lix

- Add headless openclaw node systemd service for host execution
- Migrate from nix to lix package manager
- Permit openclaw-2026.3.12 (insecure package warning)
- Use ai-worker user for node service

modules/nixos/services/openclaw_node.nix

@@ -0,0 +1,69 @@
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.services.openclaw-node;
+  openclawPkg = pkgs.openclaw;
+in {
+  options.services.openclaw-node = {
+    enable = lib.mkEnableOption "OpenClaw Node service";
+
+    user = lib.mkOption {
+      type = lib.types.str;
+      default = "ai-worker";
+      description = "User to run the OpenClaw headless node as.";
+    };
+
+    gatewayHost = lib.mkOption {
+      type = lib.types.str;
+      default = "127.0.0.1";
+      description = "Gateway host (IP or hostname).";
+    };
+
+    gatewayPort = lib.mkOption {
+      type = lib.types.int;
+      default = 18789;
+      description = "Gateway WebSocket port.";
+    };
+
+    gatewayTokenFile = lib.mkOption {
+      type = lib.types.str;
+      default = "";
+      description = "Path to file containing the gateway auth token.";
+    };
+
+    displayName = lib.mkOption {
+      type = lib.types.str;
+      default = "lazyworkhorse-host";
+      description = "Display name for this node (shown in pairing).";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    systemd.services.openclaw-node = {
+      description = "OpenClaw Headless Node Service";
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+
+      serviceConfig = {
+        Type = "exec";
+        User = cfg.user;
+        Group = cfg.user;
+        WorkingDirectory = "/var/lib/${cfg.user}";
+        ExecStart = ''
+          ${openclawPkg}/bin/openclaw \
+            node run \
+            --host ${cfg.gatewayHost} \
+            --port ${toString cfg.gatewayPort} \
+            --display-name "${cfg.displayName}"
+        '';
+        Restart = "on-failure";
+        RestartSec = 10;
+      };
+
+      environment = {
+        OPENCLAW_GATEWAY_TOKEN_FILE = cfg.gatewayTokenFile;
+        NODE_ENV = "production";
+      };
+    };
+  };
+}