direnv: use nix-direnv instead ad hoc hack

profiles/core/default.nix

@@ -124,6 +124,8 @@ in
     extraOptions = ''
       experimental-features = nix-command flakes ca-references
       min-free = 536870912
+      keep-outputs = true
+      keep-derivations = true
     '';
 
   };

users/profiles/direnv/default.nix

@@ -1,14 +1,6 @@
 {
   programs.direnv = {
     enable = true;
-    stdlib = ''
-      use_flake() {
-        mkdir -p $(direnv_layout_dir)
-        watch_file flake.nix
-        watch_file flake.lock
-        eval "$(nix print-dev-env --profile "$(direnv_layout_dir)/flake-profile")" \
-         && IN_NIX_SHELL="pure"
-      }
-    '';
+    enableNixDirenvIntegration = true;
   };
 }