base/nix: cleanup + improve eval speed

modules/base/nix/environment.nix

···
-{
-  lib,
-  pkgs,
-  config,
-  ...
-}:
-let
-  inherit (lib)
-    elem
-    pipe
-    optionals
-    filterAttrs
-    mapAttrs'
-    mkForce
-    ;
-
-  commonPaths = [
-    "nixpkgs"
-    "tgirlpkgs"
-  ]
-  ++ optionals pkgs.stdenv.hostPlatform.isDarwin [
-    "nix-darwin"
-  ];
-in
+{ lib, ... }:
 {
-  environment = {
-    # https://github.com/NixOS/nixpkgs/blob/eca4605163a534aed1981de0f5f1d7d7639d1640/nixos/modules/programs/environment.nix#L18
-    variables.NIXPKGS_CONFIG = mkForce "";
-
-    # something something backwards compatibility something something nix channels
-    etc = pipe config.nix.registry [
-      (filterAttrs (name: _: elem name commonPaths))
-      (mapAttrs' (
-        name: value: {
-          name = "nix/path/${name}";
-          value.source = value.flake;
-        }
-      ))
-    ];
-  };
+  # https://github.com/NixOS/nixpkgs/blob/eca4605163a534aed1981de0f5f1d7d7639d1640/nixos/modules/programs/environment.nix#L18
+  environment.variables.NIXPKGS_CONFIG = lib.mkForce "";
 }

modules/base/nix/substituters.nix

···
   lib,
   config,
   _class,
+  options,
   ...
 }:
 let
   inherit (lib) optionals;
 
   # well well well
-  hasCtp = if _class == "darwin" then true else (config ? catppuccin && config.catppuccin.enable);
+  hasCtp = if _class == "darwin" then true else (options ? catppuccin && config.catppuccin.enable);
 in
 {
   tgirlpkgs.cache.enable = true;