fix(messaging, ios): read isRegisteredForRemoteNotifications on main queue in getConstants

[roidayan1]

Description

Under the New Architecture, getConstants on an iOS TurboModule is invoked synchronously on the JS thread. RNFBMessagingModule's messagingConstantsDictionary (behind constantsToExport / getConstants) reads -[UIApplication isRegisteredForRemoteNotifications], and UIApplication is main-thread only. The module's requiresMainQueueSetup returns NO, so nothing moves this read onto main.

When the app runs under the Xcode debugger on a physical device, Main Thread Checker reports this on every launch:

Main Thread Checker: UI API called on a background thread: -[UIApplication isRegisteredForRemoteNotifications]

The backtrace, on thread com.facebook.react.runtime.JavaScript:

-[RNFBMessagingModule messagingConstantsDictionary]
-[RNFBMessagingModule constantsToExport]
-[RNFBMessagingModule getConstants]
facebook::react::ObjCTurboModule::performMethodInvocation

Fix: read that one value through React Native's RCTUnsafeExecuteOnMainQueueSync (from <React/RCTUtils.h>, which this file already imports). The helper runs the block inline when the caller is already on main. This is the explicit per-call dispatch that NewArch-AD-9 prescribes ("Any genuinely main-thread/UIKit work in getConstants/init is dispatched explicitly to the main queue"). initializeApp in RNFBAppModule already uses the same pattern. requiresMainQueueSetup stays NO, and the TARGET_IPHONE_SIMULATOR branch is unchanged.

Scope notes:

• Like any synchronous hop to main, this blocks the JS thread until main runs the block. It is a single property read. React Native uses the same mechanism for main-queue module constants.
• The other isRegisteredForRemoteNotifications reads, in getToken, getAPNSToken and registerForRemoteNotifications, are untouched. This PR only covers the getConstants path that Main Thread Checker flagged.

Related issues

None found. I searched for isRegisteredForRemoteNotifications, "Main Thread Checker" and "UI API called on a background thread". The closest match is #507 (closed, 2017), which is about a different call, registerForRemoteNotifications.

Release Summary

fix(messaging, ios): read isRegisteredForRemoteNotifications on the main queue when building module constants, which stops the Main Thread Checker warning under the New Architecture.

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
  • Yes
• My change supports the following platforms;
  • Android
  • iOS
  • Other (macOS, web)
• My change includes tests;
  • e2e tests added or updated in packages/\*\*/e2e
  • jest tests added or updated in packages/\*\*/__tests__
• I have updated TypeScript types that are affected by my change.
• This is a breaking change;
  • Yes
  • No

The change is iOS-only because Android has no equivalent main-thread read. There are no API or type changes: the constant has the same name, type and value.

Test Plan

• Ran the repo's iOS format check on the changed file (the same flags as yarn lint:ios:check) with the lockfile's clang-format@1.8.0 (clang-format 15.0.0): clang-format --style=Google -n -Werror packages/messaging/ios/RNFBMessaging/RNFBMessagingModule.mm. It passes.
• The Main Thread Checker report and backtrace above come from a New Architecture app on a physical iOS device under the Xcode debugger.
• I did not build or run the repo's e2e or XCTest suites against this branch, and I have not re-run the device check with this exact patch applied. CI and reviewers should confirm those.

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