Fix SWC config to preserve class names for Stimulus compatibility

Add keepClassNames: true to SWC configuration to ensure Stimulus controllers work correctly. Without this setting, class names are mangled during transpilation, breaking Stimulus functionality. This fixes failing RSpec tests for Turbo/Stimulus form submission. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

config/swc.config.js

@@ -3,6 +3,10 @@ const { env } = require('shakapacker');
 const customConfig = {
  options: {
  jsc: {
+ keepClassNames: true,
+ loose: false,
+ externalHelpers: false,
+ target: 'es2015',
  transform: {
  react: {
  refresh: env.isDevelopment && env.runningWebpackDevServer,