[Xcode 26.4] React Native 0.86.0 Release build emits public-header and deprecation warnings #57524

Description

A clean iOS Release simulator build using the React Native 0.86.0 prebuilt dependency path emits repeated warnings from React Native public headers and XCFramework module metadata under Xcode 26.4.1. Source-level declaration fixes make the same build warning-free without warning flags or log filtering.

Environment

• React Native: 0.86.0
• Expo: 57.0.4
• Xcode: 26.4.1
• SDK: iOS 26.2 simulator
• configuration: Release, Hermes, new architecture

Reproduction

1. Generate a clean iOS project using React Native 0.86.0 and the prebuilt React Native dependency path.
2. Build the workspace with xcodebuild -configuration Release -sdk iphonesimulator CODE_SIGNING_ALLOWED=NO build.
3. Inspect the unfiltered build log.

Warning categories

• missing nullability in RCTHTTPRequestHandler.h, RCTMultipartDataTask.h, and RCTWebSocketModule.h
• declarations lacking the deprecation attributes already implied by their legacy API role, including RCTAppSetupDefaultJsExecutorFactory, RCTUIConfiguratorProtocol, modal-host delegate methods, and RCTShadowView.rootView
• ShadowViewMutation overloads documented as deprecated but lacking C++ [[deprecated]] attributes
• prebuilt React XCFramework module metadata declaring a broad umbrella that produces repeated incomplete-umbrella diagnostics

Expected behavior

The pinned prebuilt React Native 0.86.0 Release build should emit no compiler or module metadata warnings with Xcode 26.4.1. Public headers should have explicit nullability and declaration attributes should match the intended API lifecycle.

I can split this into focused patches by header/module metadata surface if that is preferable.