Monorepo migration and modern runtime requirements

@sanity/assist has been ported to the Sanity plugins monorepo. This major release brings several breaking changes as part of the migration, while keeping all existing plugin functionality intact.

Please review the list of breaking changes below before upgrading.

• React Compiler enabled: The plugin is now optimized with React Compiler for improved performance.
• ESM-only: CommonJS is no longer supported. The dual module format has been removed.
• Sanity Studio v5 required: The plugin now requires Sanity Studio v5 as the minimum baseline.
• React 19 required: Updated to support React 19.2+. Learn more in our upgrade guide.
• Stricter TypeScript: Updated type definitions with improved type safety.
• Updated dependencies: All dependencies updated to latest compatible versions.

If you are not yet on Studio v5 or React 19, you should remain on @sanity/assist v4.x until you upgrade.