chore(module): wrap soonix script already in shell hook

makes it more flexible and should thus work everywhere (also in
pkgs.mkShell shellHook)

lib/module.nix

@@ -4,7 +4,7 @@
   lib,
   ...
 }: let
-  inherit (lib) types mkOption concatMapStringsSep;
+  inherit (lib) types mkOption concatMapStringsSep mapAttrsToList;
   soonix_lib = import ./. {inherit pkgs;};
   inherit (soonix_lib) engines buildAllFiles;
 in {
@@ -253,6 +253,7 @@ in {
       builtins.addErrorContext "[soonix] while generating shell hook"
       # sh
       ''
+        function _soonix() {
           CHECK_MODE=''${CHECK_MODE:-false}
           SKIP_GITIGNORE=''${SKIP_GITIGNORE:-false}
 
@@ -313,10 +314,13 @@ in {
           if [[ $status -ne 0 ]]; then
             exit $status
           fi
+        }
+        _soonix
+        unset _soonix
       '';
 
     allFiles =
-      lib.mapAttrsToList (name: hook: {
+      mapAttrsToList (name: hook: {
         src = hook.generatedDerivation;
         path = hook.output;
       })
@@ -415,18 +419,12 @@ in {
           '') (builtins.attrNames hooks)}
               ;;
             update)
-              function _soonix() {
               ${generateShellHook}
-              }
-              _soonix
               ;;
             check)
               CHECK_MODE=true
               echo "Checking files..."
-              function _soonix() {
               ${generateShellHook}
-              }
-              _soonix
               ;;
             esac
         '';