feat: add nixos configuration

nixos/modules/packages/development.nix

@@ -0,0 +1,29 @@
+{ codexPkgs, pkgs, ... }:
+
+{
+  environment.systemPackages = with pkgs; [
+    clang
+    cmake
+    codexPkgs.codex
+    gcc
+    git
+    gitui
+    meson
+    neovim
+    ninja
+    tree-sitter
+    vim
+  ];
+
+  systemd.user.services.codex-background-server = {
+    description = "Codex background app server";
+    wantedBy = [ "default.target" ];
+    unitConfig.ConditionUser = "hhhh";
+    serviceConfig = {
+      ExecStart = "/run/current-system/sw/bin/codex app-server --listen unix://";
+      WorkingDirectory = "%h";
+      Restart = "on-failure";
+      RestartSec = 3;
+    };
+  };
+}