Description

This PR updates the peer dependency constraints for React and React-DOM to support React 19.x versions. The changes modify both the main package.json and the React flavor template to expand the accepted React version range from >=16.8.0 <19 to >=16.8.0 <20, enabling compatibility with React 19 while maintaining backward compatibility with all previously supported React versions.

Motivation and Context

Fixes #10243

How Has This Been Tested?

• Ran the full unit test suite (npm run test:unit)
• All 795 tests passed, 12 skipped (no failures)

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.