React19 Concurrent Patterns

This is the boring but essential companion to your React 19 migration. It keeps you from accidentally breaking the concurrent patterns you already have working (useTransition, useDeferredValue, Suspense) while the main migration rewrites forwardRef and defaultProps. The skill splits cleanly into preserve versus adopt: leave your React 18 concurrent code completely untouched during migration, then consider the new APIs like use() and useOptimistic afterward. The grep command at the end is genuinely useful for verifying the migrator didn't mess with your transition logic. If you're migrating a codebase that already leans on concurrent features, this prevents painful regressions.