Revert unnecessary file extension changes

- Revert babel.config.cjs back to babel.config.js (CommonJS works fine in workspace)
- Remove unnecessary React/TypeScript presets from babel config
- Update knip.ts to reference correct babel config path
- Keep jest.config.mjs (ES module extension is actually required)

Testing confirmed:
- babel.config.js works with CommonJS syntax in workspace package
- React/TypeScript presets were unnecessary (ts-jest handles JSX/TSX)
- All tests pass with simplified configuration
- jest.config.js extension causes "Cannot use import statement" error

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

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

Author: AbanoubGhadban

knip.ts

@@ -26,7 +26,7 @@ const config: KnipConfig = {
         '!packages/react-on-rails/lib/**',
       ],
       babel: {
-        config: ['packages/react-on-rails/babel.config.cjs'],
+        config: ['packages/react-on-rails/babel.config.js'],
       },
       ignore: [
         'packages/react-on-rails/tests/emptyForTesting.js',

packages/react-on-rails/babel.config.cjs

@@ -0,0 +1,3 @@
+module.exports = {
+  presets: [['@babel/preset-env', { targets: { node: 'current' } }]],
+};