React 19.2 is here: Activity API, useEffectEvent and more

React 19.2 introduces the Activity API for efficiently hiding and restoring UI state without unmounting components, and the useEffectEvent Hook for creating stable event handlers that access latest state without dependency array issues. The release includes cacheSignal API for managing cached fetch lifetimes, partial pre-rendering for faster initial loads, batched Suspense boundary reveals for SSR, and Performance Tracks in Chrome DevTools. Additional improvements include updated ESLint rules with flat config support, Web Streams API support for Node.js, and a new useId prefix format for better CSS compatibility.