refactor(flake): split host guest and module assembly

flake.nix

@@ -76,14 +76,13 @@
     { self, nixpkgs, ... }@inputs:
     let
       inherit (nixpkgs) lib;
-      my = import ./lib { inherit lib inputs self; };
+      flake = import ./flake { inherit lib inputs self; };
     in
     {
-      # Helper functions for discovering and building hosts.
-      lib = my;
-
       # Every host under hosts/ is discovered and built.
-      nixosConfigurations = my.mkHosts (self + "/hosts");
+      nixosConfigurations = flake.mkHosts {
+        root = self + "/hosts";
+      };
 
       # A project shell for agent-local resources that should travel with this
       # checkout rather than the operator's global profile.