Fix RSC test infrastructure and add TODO explaining temporary disable

- Add TODO message explaining why RSC tests are temporarily disabled
  (jest.setup.js uses require() incompatible with ESM mode)
- Fix utils.test.js import path: testUtils.js -> testUtils.ts
  (was causing "Cannot find module" error)

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

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

Author: justin808

packages/react-on-rails-pro/package.json

@@ -9,7 +9,7 @@
     "clean": "rm -rf ./lib",
     "test": "yarn test:non-rsc && yarn test:rsc",
     "test:non-rsc": "jest tests --testPathIgnorePatterns=\".*(RSC|stream|registerServerComponent|serverRenderReactComponent|SuspenseHydration).*\"",
-    "test:rsc": "exit 0",
+    "test:rsc": "echo 'TODO: RSC tests disabled - jest.setup.js uses require() incompatible with ESM mode. Re-enable after converting setup to ESM.' && exit 0",
     "type-check": "yarn run tsc --noEmit --noErrorTruncation",
     "prepare": "[ -f lib/ReactOnRails.full.js ] || (rm -rf ./lib && tsc)",
     "prepublishOnly": "yarn run build",

packages/react-on-rails-pro/tests/utils.test.js

@@ -1,7 +1,7 @@
 import { enableFetchMocks } from 'jest-fetch-mock';
 
 import { fetch } from '../src/utils.ts';
-import { createNodeReadableStream, getNodeVersion } from './testUtils.js';
+import { createNodeReadableStream, getNodeVersion } from './testUtils.ts';
 
 enableFetchMocks();