Next.js v16.2.0-canary.56: Prefetch fixes and React sync v16.2.0-canary.56

Shipped some solid prefetch improvements, nailed down runtime byte stripping when deployed, and bumped React to the latest. Also cracked sync IO validation in generateMetadata so it actually respects your page's prefetchable status. Nothing earth-shattering, just the kind of stuff that makes your build less angry.