fix(cms): extract serverFunction to separate 'use server' file for Next.js 15.5 server action registration

apps/cms/src/app/(payload)/layout.tsx

@@ -2,26 +2,17 @@
 /* DO NOT MODIFY IT BECAUSE IT COULD BE REWRITTEN AT ANY TIME. */
 import config from "@payload-config";
 import "@payloadcms/next/css";
-import type { ServerFunctionClient } from "payload";
-import { handleServerFunctions, RootLayout } from "@payloadcms/next/layouts";
+import { RootLayout } from "@payloadcms/next/layouts";
 import React from "react";
 
 import { importMap } from "./admin/importMap.js";
+import { serverFunction } from "./serverFunction";
 import "./custom.scss";
 
 type Args = {
   children: React.ReactNode;
 };
 
-const serverFunction: ServerFunctionClient = async function (args) {
-  "use server";
-  return handleServerFunctions({
-    ...args,
-    config,
-    importMap,
-  });
-};
-
 const Layout = ({ children }: Args) => (
   <RootLayout
     config={config}

apps/cms/src/app/(payload)/serverFunction.ts

@@ -0,0 +1,14 @@
+"use server";
+
+import config from "@payload-config";
+import { handleServerFunctions } from "@payloadcms/next/layouts";
+import { importMap } from "./admin/importMap.js";
+import type { ServerFunctionClient } from "payload";
+
+export const serverFunction: ServerFunctionClient = async (args) => {
+  return handleServerFunctions({
+    ...args,
+    config,
+    importMap,
+  });
+};