Include RSC bundle in default webpack build

The default branch (no env vars) runs during bin/shakapacker for
production/CI builds. Without the RSC config in the array, the RSC
bundle only gets built when RSC_BUNDLE_ONLY is set (dev watchers).
Production deploys + CI would miss it.

The *_BUNDLE_ONLY gates remain for dev Procfile processes (each
watcher builds one bundle in isolation).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: ihabadham

config/webpack/webpackConfig.js

@@ -28,10 +28,9 @@ const webpackConfig = (envSpecific) => {
     console.log('[React on Rails] Creating only the RSC bundle.');
     result = rscWebpackConfig();
   } else {
-    // default is the standard client and server build
     // eslint-disable-next-line no-console
-    console.log('[React on Rails] Creating both client and server bundles.');
-    result = [clientConfig, serverConfig];
+    console.log('[React on Rails] Creating client, server, and RSC bundles.');
+    result = [clientConfig, serverConfig, rscWebpackConfig()];
   }
 
   // To debug, uncomment next line and inspect "result"