Add AccessibilityInfo.isDifferentiateWithoutColorEnabled on iOS

[camilopires]

Summary:

Differentiate Without Color asks apps not to rely on colour alone, for example by adding icons or patterns to status colours and validation states. React Native apps can't currently detect this setting.

This adds AccessibilityInfo.isDifferentiateWithoutColorEnabled() and a differentiateWithoutColorChanged event, following the existing isDarkerSystemColorsEnabled pattern. It reads UIAccessibilityShouldDifferentiateWithoutColor() and observes UIAccessibilityShouldDifferentiateWithoutColorDidChangeNotification. On Android, the method resolves to false.

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

Changelog:

[IOS] [ADDED] - AccessibilityInfo.isDifferentiateWithoutColorEnabled() and differentiateWithoutColorChanged

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: "Differentiate Without Color is disabled."
• Turned on: "Differentiate Without Color is enabled."
• Turned off: "Differentiate Without Color is disabled."

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[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

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