Use SWC only for TypeScript, Babel for all JavaScript

Simplified approach: SWC handles only .ts and .tsx files, while Babel
handles all .js, .jsx, and .mjs files. This avoids the Stimulus
compatibility issues entirely while still using SWC for TypeScript.

This is a more maintainable solution than trying to selectively exclude
specific directories from SWC processing.

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

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

config/webpack/commonWebpackConfig.js

@@ -73,24 +73,20 @@ if (scssConfigIndex === -1) {
 const commonWebpackConfig = () => {
   const config = merge({}, baseClientWebpackConfig, commonOptions, ignoreWarningsConfig);
 
-  const controllersPath = path.resolve(__dirname, '../../client/app/controllers');
-
-  // Find and modify the SWC rule to exclude Stimulus controllers
+  // Find the SWC rule and restrict it to only TypeScript files
+  // Use Babel for all JavaScript files (SWC has compatibility issues with Stimulus)
   const swcRuleIndex = config.module.rules.findIndex(rule =>
     rule.test && /\.(ts|tsx|js|jsx|mjs|coffee)/.test(rule.test.toString())
   );
 
   if (swcRuleIndex !== -1) {
-    const originalExclude = config.module.rules[swcRuleIndex].exclude;
-    config.module.rules[swcRuleIndex].exclude = [
-      originalExclude,
-      controllersPath
-    ].filter(Boolean);
+    // Change SWC rule to only handle TypeScript files
+    config.module.rules[swcRuleIndex].test = /\.(ts|tsx)(\.erb)?$/;
 
-    // Add Babel loader specifically for Stimulus controllers
+    // Add Babel loader for all JavaScript files
     config.module.rules.push({
-      test: /\.js$/,
-      include: controllersPath,
+      test: /\.(js|jsx|mjs)(\.erb)?$/,
+      exclude: /node_modules/,
       use: {
         loader: 'babel-loader',
         options: {
@@ -101,6 +97,11 @@ const commonWebpackConfig = () => {
               modules: 'auto',
               bugfixes: true,
               exclude: ['transform-typeof-symbol']
+            }],
+            ['@babel/preset-react', {
+              runtime: 'automatic',
+              development: process.env.NODE_ENV !== 'production',
+              useBuiltIns: true
             }]
           ]
         }