fix(rsc): show warning when auto css heuristics failed

Author: hi-ogawa

packages/plugin-rsc/examples/basic/src/routes/style-server/not-detected/server.css

@@ -0,0 +1,3 @@
+.test-style-server-not-detected {
+  color: rgb(255, 165, 0);
+}

packages/plugin-rsc/examples/basic/src/routes/style-server/not-detected/server.tsx

@@ -0,0 +1,9 @@
+import './server.css'
+
+export function TestStyleServerNotDetected() {
+  return (
+    <div className="test-style-server-not-detected">
+      test-style-server-not-detected
+    </div>
+  )
+}

packages/plugin-rsc/examples/basic/src/routes/style-server/server.tsx

@@ -1,13 +1,16 @@
 import './server.css'
 import styles from './server.module.css'
+// import { TestStyleServerNotDetected } from "./not-detected/server";
 
-export function TestStyleServer() {
+export async function TestStyleServer() {
+  const { TestStyleServerNotDetected } = await import('./not-detected/server')
   return (
     <>
       <div className="test-style-server">test-style-server</div>
       <div data-testid="css-module-server" className={styles.server}>
         test-css-module-server
       </div>
+      <TestStyleServerNotDetected />
     </>
   )
 }