feat(nix): add system module, pass config to lib

This commit introduces a system module for NixOS and Home Manager,
and passes the configuration to the lib file.

nix/lib/default.nix

@@ -1,9 +1,11 @@
-{ lib, ... }:
+{ lib, config, ... }:
 let
-  inherit (lib.attrsets) concatMapAttrs;
+  cfg = config.flake;
+  inherit (lib.attrsets) mapAttrs concatMapAttrs;
 in
 {
   flake.lib = {
     flattenAttrs = attrset: concatMapAttrs (_: v: v) attrset;
+    forAllUsers = f: mapAttrs f cfg.manifest.users;
   };
 }

nix/manifest.nix

@@ -8,7 +8,6 @@ let
       };
       nixpkgs.hostPlatform = "x86_64-linux";
       boot.loader.systemd-boot.enable = true;
-      system.stateVersion = "25.05";
       networking = { inherit hostName; };
     };
 in

nix/modules/system.nix

@@ -0,0 +1,10 @@
+{
+  flake.modules.nixos.default = {
+    system.stateVersion = "25.11";
+  };
+  flake.modules.homeManager.default =
+    { osConfig, ... }:
+    {
+      home.stateVersion = osConfig.system.stateVersion;
+    };
+}

nix/modules/users.nix

@@ -1,12 +1,13 @@
 { config, lib, ... }:
 let
-  inherit (config.flake.lib) flattenAttrs;
+  cfg = config.flake;
+  inherit (config.flake.lib) forAllUsers flattenAttrs;
   inherit (lib.attrsets) filterAttrs;
-  owner = flattenAttrs (filterAttrs (_: v: (v.primary or false)) config.flake.manifest.users);
+  owner = flattenAttrs (filterAttrs (_: v: (v.primary or false)) cfg.manifest.users);
 in
 {
   flake.modules.nixos.default =
-    { pkgs, ... }:
+    { pkgs, config, ... }:
     {
       #TODO: move sudo/security options elsewhere
       security.sudo.wheelNeedsPassword = false;
@@ -26,5 +27,12 @@ in
           openssh.authorizedKeys.keys = [ owner.pubkey ];
         };
       };
+      home-manager.users = forAllUsers (
+        name: _: {
+          #TODO: move into nixos/darwin config - should not apply to homeConfigurations
+          home.username = name;
+          home.homeDirectory = config.users.users.${name}.home;
+        }
+      );
     };
 }