emacsPackages.agda2-mode: trivialBuild -> melpaBuild

This patch does not increase closure size:

> nix path-info -rSsh result/ | sort -hk3
/nix/store/7v6xff4kcrb696dyzbgywy3myv63fwsj-emacs-funcs.sh                 1.2K    1.2K
/nix/store/bihw7p4zdqwyxmnc8h67c06lnjkvdan8-xgcc-13.3.0-libgcc           155.9K  155.9K
/nix/store/vf553z7mi2vqk8ca6kkfd9x5gy3nnz0p-libunistring-1.1               1.7M    1.7M
/nix/store/pq755f1pxaas9q7666wzdzxidcvf9frg-libidn2-2.3.7                352.7K    2.1M
/nix/store/m71p7f0nymb19yn1dascklyya2i96jfw-glibc-2.39-52                 28.8M   31.0M
/nix/store/v9jyklnpicy1vzwcm41aj14qwsq5p22c-emacs-agda2-mode-2.6.4.3     804.6K   31.8M

pkgs/applications/editors/emacs/elisp-packages/manual-packages/agda2-mode/default.nix

@@ -1,29 +1,18 @@
-{ trivialBuild
+{ melpaBuild
 , haskellPackages
 }:
 let
-  Agda = haskellPackages.Agda.bin;
+  Agda = haskellPackages.Agda;
 in
-trivialBuild {
-  pname = "agda-mode";
-  version = Agda.version;
+melpaBuild {
+  pname = "agda2-mode";
+  inherit (Agda) src version;
 
-  dontUnpack = true;
-
-  # already byte-compiled by Agda builder
-  buildPhase = ''
-    agda=`${Agda}/bin/agda-mode locate`
-    cp `dirname $agda`/*.el* .
-  '';
+  files = ''("src/data/emacs-mode/*.el")'';
 
   meta = {
     inherit (Agda.meta) homepage license;
     description = "Agda2-mode for Emacs extracted from Agda package";
-    longDescription = ''
-      Wrapper packages that liberates init.el from `agda-mode locate` magic.
-      Simply add this to user profile or systemPackages and do `(require
-      'agda2)` in init.el.
-    '';
   };
 }