Add bundler auto-detection to all webpack config files

Updated client.js, server.js, and clientWebpackConfig.js to use
bundler auto-detection instead of hardcoded webpack requires.

This ensures ProvidePlugin and DefinePlugin use the correct bundler
(webpack or @rspack/core) based on shakapacker config.

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

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

Author: justin808

config/webpack/client.js

@@ -1,16 +1,21 @@
 const devBuild = process.env.NODE_ENV === 'development';
 const isHMR = process.env.WEBPACK_DEV_SERVER === 'TRUE';
 const ReactRefreshWebpackPlugin = require('@pmmmwh/react-refresh-webpack-plugin');
-const webpack = require('webpack');
+const { config } = require('shakapacker');
 const environment = require('./environment');
 
+// Auto-detect bundler from shakapacker config and load the appropriate library
+const bundler = config.assets_bundler === 'rspack'
+  ? require('@rspack/core')
+  : require('webpack');
+
 if (devBuild && !isHMR) {
   environment.loaders.get('sass').use.find((item) => item.loader === 'sass-loader').options.sourceMap = false;
 }
 
 environment.plugins.append(
   'Provide',
-  new webpack.ProvidePlugin({
+  new bundler.ProvidePlugin({
     $: 'jquery',
     jQuery: 'jquery',
     jquery: 'jquery',

config/webpack/clientWebpackConfig.js

@@ -1,14 +1,19 @@
 // The source code including full typescript support is available at:
 // https://github.com/shakacode/react_on_rails_tutorial_with_ssr_and_hmr_fast_refresh/blob/master/config/webpack/clientWebpackConfig.js
 
-const webpack = require('webpack');
+const { config } = require('shakapacker');
 const commonWebpackConfig = require('./commonWebpackConfig');
 
+// Auto-detect bundler from shakapacker config and load the appropriate library
+const bundler = config.assets_bundler === 'rspack'
+  ? require('@rspack/core')
+  : require('webpack');
+
 const configureClient = () => {
   const clientConfig = commonWebpackConfig();
 
   clientConfig.plugins.push(
-    new webpack.ProvidePlugin({
+    new bundler.ProvidePlugin({
       $: 'jquery',
       jQuery: 'jquery',
       ActionCable: '@rails/actioncable',

config/webpack/server.js

@@ -1,16 +1,20 @@
 const merge = require('webpack-merge');
 
 const devBuild = process.env.NODE_ENV === 'production' ? 'production' : 'development';
-const webpack = require('webpack');
-
+const { config } = require('shakapacker');
 const environment = require('./environment');
 
+// Auto-detect bundler from shakapacker config and load the appropriate library
+const bundler = config.assets_bundler === 'rspack'
+  ? require('@rspack/core')
+  : require('webpack');
+
 // React Server Side Rendering shakapacker config
 // Builds a Node compatible file that React on Rails can load, never served to the client.
 
 environment.plugins.insert(
   'DefinePlugin',
-  new webpack.DefinePlugin({
+  new bundler.DefinePlugin({
     TRACE_TURBOLINKS: true,
     'process.env': {
       NODE_ENV: devBuild,