Add header_mappings_dir to React-Fabric.podspec animated subspec

[zoontek]

Summary:

When building React Native (0.85.0-rc.5) core from source (RCT_USE_PREBUILT_RNCORE=0), the React-Fabric/animated CocoaPods subspec flattens the event_drivers/ subdirectory headers because header_mappings_dir is not set.

CocoaPods' header_dir without header_mappings_dir places all matched headers directly under the specified directory, losing any subdirectory structure. This means event_drivers/EventAnimationDriver.h ends up at react/renderer/animated/EventAnimationDriver.h instead of react/renderer/animated/event_drivers/EventAnimationDriver.h.

The #include in NativeAnimatedNodesManager.h expects the full path with the event_drivers/ subdirectory, so the build fails with:

'react/renderer/animated/event_drivers/EventAnimationDriver.h' file not found

This doesn't affect prebuilt (RCT_USE_PREBUILT_RNCORE=1) builds because the xcframework ships with a VFS overlay that maps headers correctly.

The fix adds header_mappings_dir to the animated subspec in React-Fabric.podspec, which tells CocoaPods to preserve the directory structure relative to react/renderer/animated.

Changelog:

[IOS] [FIXED] - Fix EventAnimationDriver.h not found when building React Native from source due to missing header_mappings_dir in React-Fabric/animated podspec

Test Plan:

1. Set RCT_USE_PREBUILT_RNCORE=0 in your Podfile
2. Run pod install
3. Build the project — previously fails with 'react/renderer/animated/event_drivers/EventAnimationDriver.h' file not found
4. With this fix, the build succeeds

[meta-codesync]

@zeyap has imported this pull request. If you are a Meta employee, you can view this in D97295771.

[zeyap]

thanks for fixing it!