feat(services): add hermes-agent nixos module

modules/nixos/services/hermes-agent.nix

@@ -0,0 +1,38 @@
+{ inputs, ... }: {
+  flake.modules.nixos.services =
+    {
+      config,
+      lib,
+      options,
+      userName,
+      ...
+    }:
+    with lib;
+    let
+      cfg = config.tnix.services.hermes-agent;
+    in
+    {
+      imports = [
+        inputs.hermes-agent.nixosModules.default
+      ];
+
+      options.tnix.services.hermes-agent = {
+        enable = mkEnableOption "Hermes Agent";
+        environmentFiles = options.services.hermes-agent.environmentFiles;
+      };
+
+      config = mkIf cfg.enable {
+        services.hermes-agent = {
+          enable = true;
+          settings.model = {
+            provider = "opencode-go";
+            default = "deepseek-v4-flash";
+          };
+          environmentFiles = cfg.environmentFiles;
+          addToSystemPackages = true;
+        };
+
+        users.users.${userName}.extraGroups = [ "hermes" ];
+      };
+    };
+}