Fix ExecJS compatibility: remove libraryTarget commonjs2 for default setup

Root cause: Setting libraryTarget: 'commonjs2' creates bundles that require
Node.js's require() function, which is not available in ExecJS (the default
server rendering engine).

Changes:
- Removed libraryTarget: 'commonjs2' from spec/dummy (uses ExecJS)
- Removed libraryTarget: 'commonjs2' from execjs-compatible-dummy
- Updated generator template with clear comments about when to use it
- Kept target: 'node' to externalize Node.js built-in modules (required for React 19)

The fix:
- target: 'node' externalizes crypto, async_hooks, stream (✅ needed for React 19)
- libraryTarget: 'commonjs2' only for Node renderer (❌ breaks ExecJS)

Fixes CI errors:
- TypeError: require is not a function (ExecJS evaluation error)
- examples (3.4, latest)
- examples (3.2, minimum)
- dummy-app-integration-tests

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

lib/generators/react_on_rails/templates/base/base/config/webpack/serverWebpackConfig.js.tt

@@ -50,8 +50,10 @@ const configureServer = () => {
   serverWebpackConfig.output = {
     filename: 'server-bundle.js',
     globalObject: 'this',
-    // React 19 requires commonjs2 for proper Node.js module resolution
-    libraryTarget: 'commonjs2',
+    // Note: libraryTarget should only be 'commonjs2' when using Node renderer
+    // For ExecJS (default), leave it undefined to allow proper evaluation
+    // If using the React on Rails Pro node server renderer, uncomment the next line
+    // libraryTarget: 'commonjs2',
     path: require('path').resolve(__dirname, '../../ssr-generated'),
     // No publicPath needed since server bundles are not served via web
     // https://webpack.js.org/configuration/output/#outputglobalobject

react_on_rails_pro/spec/execjs-compatible-dummy/config/webpack/serverWebpackConfig.js

@@ -48,9 +48,10 @@ const configureServer = () => {
   serverWebpackConfig.output = {
     filename: 'server-bundle.js',
     globalObject: 'this',
+    // Note: libraryTarget should only be 'commonjs2' when using Node renderer
+    // For ExecJS (default), leave it undefined to allow proper evaluation
     // If using the React on Rails Pro node server renderer, uncomment the next line
-    // React 19 requires commonjs2 for proper Node.js module resolution
-    libraryTarget: 'commonjs2',
+    // libraryTarget: 'commonjs2',
     path: config.outputPath,
     publicPath: config.publicPath,
     // https://webpack.js.org/configuration/output/#outputglobalobject

spec/dummy/config/webpack/serverWebpackConfig.js

@@ -45,8 +45,10 @@ const configureServer = () => {
   serverWebpackConfig.output = {
     filename: 'server-bundle.js',
     globalObject: 'this',
-    // React 19 requires commonjs2 for proper Node.js module resolution
-    libraryTarget: 'commonjs2',
+    // Note: libraryTarget should only be 'commonjs2' when using Node renderer
+    // For ExecJS (default), leave it undefined to allow proper evaluation
+    // If using the React on Rails Pro node server renderer, uncomment the next line
+    // libraryTarget: 'commonjs2',
     path: config.outputPath,
     publicPath: config.publicPath,
     // https://webpack.js.org/configuration/output/#outputglobalobject