Keep react-native/setup-env reachable in the module graph

[cipolleschi]

Summary

#57475 pointed Metro's getModulesRunBeforeMainModule at react-native/setup-env (src/setup-env.js) instead of InitializeCore.

But Metro's serializer only emits a run-before-main require for modules already in the bundle graph — see getAppendScripts:

const paths = [...options.runBeforeMainModule, entryPoint];
for (const path of paths) {
  if (modules.some(module => module.path === path)) { /* emit run stmt */ }
}

Nothing imports src/setup-env.js at runtime, so it was silently dropped. The RN environment setup (setUpDefaultReactNativeEnvironment: HMRClient, timers, batched bridge, AppRegistry setup, …) then never ran before the app's main module, and the app redboxed on launch:

Error: Failed to call into JavaScript module method HMRClient.setup().
Module has not been registered as callable.
Registered callable JavaScript modules (n = 1): AppRegistry.

This broke the template E2E tests on both iOS and Android — the app renders a redbox, so Maestro's assertVisible: 'Welcome to React Native' fails (the test (…) jobs are green only because the Maestro step runs with continue-on-error: true; the real failure surfaces via the retry chain and the retry_2 / report job).

Fix

Have the deprecated InitializeCore delegate to 'react-native/setup-env' via a side-effectful require. InitializeCore is a guaranteed graph entry (renderer → ReactNativePrivateInitializeCore → InitializeCore), so this pulls src/setup-env.js into the graph, and getModulesRunBeforeMainModule runs it before the main module again.

Behavior is unchanged: setup-env and InitializeCore both call the idempotent setUpDefaultReactNativeEnvironment(). This keeps #57475's move to setup-env intact rather than reverting it.

Changelog:

[General][Fixed] - Fix app failing to initialize (HMRClient.setup() redbox) because the environment setup module was dropped from the bundle

Test Plan

• Template E2E (test_e2e_ios_templateapp / test_e2e_android_templateapp) should pass: app launches and shows "Welcome to React Native" instead of the redbox.

cc @huntie (#57475)

[huntie]

Thanks for this catch 🙏🏻

Edit: Just making sure why InitializeCore.js does get depended on as I can't see a code reference. But if E2E tests pass then let's land.

Edit 2: Found it!: https://github.com/react/react/blob/5123b063a7b3cd5c42ea2be2ccebe4e68d8b12e3/packages/react-native-renderer/src/ReactNativeInjectionShared.js#L17

[meta-codesync]

@huntie has imported this pull request. If you are a Meta employee, you can view this in D111226610.