add stable nixpkgs to flake registry

flake.lock

@@ -355,6 +355,22 @@
         "type": "github"
       }
     },
+    "nixpkgs-stable": {
+      "locked": {
+        "lastModified": 1775811116,
+        "narHash": "sha256-t+HZK42pB6N+i5RGbuy7Xluez/VvWbembBdvzsc23Ss=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "54170c54449ea4d6725efd30d719c5e505f1c10e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-25.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "nixpkgs_2": {
       "locked": {
         "lastModified": 1774935083,
@@ -404,6 +420,7 @@
         "lanzaboote": "lanzaboote",
         "nixos-hardware": "nixos-hardware",
         "nixpkgs": "nixpkgs",
+        "nixpkgs-stable": "nixpkgs-stable",
         "simple-nixos-mailserver": "simple-nixos-mailserver",
         "vscode-extensions": "vscode-extensions"
       }

flake.nix

@@ -1,6 +1,7 @@
 {
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    nixpkgs-stable.url = "github:NixOS/nixpkgs/nixos-25.11";
     nixos-hardware.url = "github:NixOS/nixos-hardware/master";
     colmena = {
       url = "github:zhaofengli/colmena";
@@ -42,6 +43,7 @@
       home-manager,
       lanzaboote,
       nixos-hardware,
+      nixpkgs-stable,
       nixpkgs,
       simple-nixos-mailserver,
       vscode-extensions,

mod/common/nix.nix

@@ -16,8 +16,9 @@ with lib;
       auto-optimise-store = true;
     };
     nix.registry = {
-      hd.flake = inputs.self;
+      cfg.flake = inputs.self;
       nixpkgs.flake = inputs.nixpkgs;
+      nixpkgs-stable.flake = inputs.nixpkgs-stable;
     };
     nixpkgs.config.allowUnfree = false;
   };