feat: initial nix package and NixOS module for hermes-agent v0.2.0

- buildPythonApplication with Python 3.12
- All extras included (messaging, cron, tts, voice, mcp, honcho, acp)
- Custom PyPI packages: fal-client, honcho-ai, agent-client-protocol
- NixOS module with systemd service for gateway mode
- Runtime deps wrapped: nodejs 22, ripgrep, ffmpeg, git
- Flake-based with overlay support

flake.nix

@@ -0,0 +1,34 @@
+{
+  description = "Nix package and NixOS module for Hermes Agent by Nous Research";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+      in
+      {
+        packages = {
+          hermes-agent = pkgs.callPackage ./package.nix { };
+          default = self.packages.${system}.hermes-agent;
+        };
+
+        devShells.default = pkgs.mkShell {
+          packages = [ self.packages.${system}.hermes-agent ];
+        };
+      }
+    ) // {
+      nixosModules = {
+        hermes-agent = import ./module.nix self;
+        default = self.nixosModules.hermes-agent;
+      };
+
+      overlays.default = final: prev: {
+        hermes-agent = final.callPackage ./package.nix { };
+      };
+    };
+}