feat(nixos): integrate agent VM into host configurations

flake.nix

@@ -3,6 +3,15 @@
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-26.05";
+    agent-nixpkgs.url = "tarball+https://mirrors.cernet.edu.cn/nix-channels/nixos-26.05/nixexprs.tar.xz";
+    nixpkgs-unstable.url = "tarball+https://mirrors.cernet.edu.cn/nix-channels/nixos-unstable/nixexprs.tar.xz";
+    # Exact revisions of the source archives previously used on agent.
+    hermes-agent.url = "github:NousResearch/hermes-agent/3f2afed3eb813cb00bd381d29b084d0e01de048f";
+    omp.url = "github:can1357/oh-my-pi/08542ed0df02ecaa78aaab28388aa6a563045f16";
+    herdr-nix = {
+      url = "github:herdrdev/herdr-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
 
     home-manager = {
       url = "github:nix-community/home-manager/release-26.05";
@@ -14,6 +23,11 @@
       url = "github:nix-community/nix4nvchad";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+    # Keep the agent VM on its currently installed NvChad module revision.
+    agent-nix4nvchad = {
+      url = "github:nix-community/nix4nvchad/042bbb1be519d01c76d8c65b2e004212b5b706ad";
+      inputs.nixpkgs.follows = "agent-nixpkgs";
+    };
 
     # NixOS WSL
     nixos-wsl = {
@@ -31,17 +45,25 @@
     };
   };
 
-  outputs = inputs@{ nixpkgs, home-manager, ... }:
-  let
-    username = "luochen570";
-    hosts = import ./lib/hosts.nix;
-    mkHost = import ./lib/mkHost.nix {
-      inherit nixpkgs home-manager inputs;
+  outputs =
+    inputs@{ nixpkgs, home-manager, ... }:
+    let
+      username = "luochen570";
+      hosts = import ./lib/hosts.nix;
+      mkConfiguredHost =
+        hostname: cfg:
+        (import ./lib/mkHost.nix {
+          nixpkgs = if hostname == "agent" then inputs.agent-nixpkgs else nixpkgs;
+          inherit home-manager inputs;
+        })
+          (
+            {
+              inherit hostname username;
+            }
+            // cfg
+          );
+    in
+    {
+      nixosConfigurations = nixpkgs.lib.mapAttrs mkConfiguredHost hosts;
     };
-    mkConfiguredHost = hostname: cfg: mkHost ({
-      inherit hostname username;
-    } // cfg);
-  in {
-    nixosConfigurations = nixpkgs.lib.mapAttrs mkConfiguredHost hosts;
-  };
 }