feat(iOS): Enable synchronous screen shadow state updates by default

[kmichalikk]

Description

This PR changes the default value for synchronousScreenUpdatesEnabled flag to true

Changes

Updated default values for the flag in native hierarchy & JS.

Before & after - visual documentation

N/A

Test plan

See #3282

Checklist

• Included code example that can be used to test this change.
• For visual changes, included screenshots / GIFs / recordings documenting the change.
• For API changes, updated relevant public types.
• Ensured that CI passes

[Copilot]

Pull request overview

Enables synchronous screen shadow state updates by default (via synchronousScreenUpdatesEnabled = true) to improve iOS behavior for Fabric/native stack scenarios that benefit from immediate state propagation.

Changes:

• Flips the default for synchronousScreenUpdatesEnabled to true in the JS feature flags.
• Updates Fabric codegen defaults so synchronousShadowStateUpdatesEnabled defaults to true for RNSScreen and RNSModalScreen.
• Sets the iOS native screen view’s internal default (_synchronousShadowStateUpdatesEnabled) to YES.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/flags.ts	Changes the JS feature flag default to enable synchronous screen updates by default.
src/fabric/ScreenNativeComponent.ts	Updates Fabric codegen default prop for synchronous shadow state updates on RNSScreen.
src/fabric/ModalScreenNativeComponent.ts	Updates Fabric codegen default prop for synchronous shadow state updates on RNSModalScreen.
ios/RNSScreen.mm	Sets the native iOS default for _synchronousShadowStateUpdatesEnabled to enabled.
FabricExample/App.tsx	Aligns the example app’s flag configuration with the new default.

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