Add AccessibilityInfo.isOnOffSwitchLabelsEnabled on iOS

[camilopires]

Summary:

On/Off Labels adds I/O glyphs to switches. UISwitch shows them automatically, but custom toggles built from Pressable or View can't. React Native apps can't currently detect this setting.

This adds AccessibilityInfo.isOnOffSwitchLabelsEnabled() and a onOffSwitchLabelsChanged event, following the existing isDarkerSystemColorsEnabled pattern. It reads UIAccessibilityIsOnOffSwitchLabelsEnabled() and observes UIAccessibilityOnOffSwitchLabelsDidChangeNotification. On Android, the method resolves to false.

Discussion: react-native-community/discussions-and-proposals#1026

Changelog:

[IOS] [ADDED] - AccessibilityInfo.isOnOffSwitchLabelsEnabled() and onOffSwitchLabelsChanged

Test Plan:

• yarn jest packages/react-native/Libraries/Components/AccessibilityInfo: all tests pass
• yarn flow-check: 0 errors
• yarn lint: passes
• yarn build-types --validate: API snapshot up to date
• yarn test-generated-typescript and yarn test-typescript-legacy: pass
• yarn format-check-cpp: passes
• RNTester builds for the iOS simulator using Xcode 27.1

On an iPhone 18 Pro simulator running iOS 27.0: I flipped the setting in the simulator's Settings app with a throwaway XCUITest, not part of this PR, and read RNTester's Accessibility → "Check if the display options are enabled" row. RNTester stayed running the whole time, so the row could only update through the change event.

• Before: "On/Off Labels is disabled."
• Turned on: "On/Off Labels is enabled."
• Turned off: "On/Off Labels is disabled."

[meta-cla]

Hi @camilopires!

Thank you for your pull request and welcome to our community.

Action Required

In order to merge any pull request (code, docs, etc.), we require contributors to sign our Contributor License Agreement, and we don't seem to have one on file for you.

Process

In order for us to review and merge your suggested changes, please sign at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need to sign the corporate CLA.

Once the CLA is signed, our tooling will perform checks and validations. Afterwards, the pull request will be tagged with CLA signed. The tagging process may take up to 1 hour after signing. Please give it that time before contacting us about it.

If you have received this in error or have any questions, please contact us at cla@meta.com. Thanks!

[github-actions]

Warning

JavaScript API change detected

This PR commits an update to ReactNativeApi.d.ts, indicating a change to React Native's public JavaScript API.

• Please include a clear changelog message.
• This change will be subject to additional review.

This change was flagged as: POTENTIALLY_BREAKING

[meta-cla]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Meta Open Source project. Thanks!