Use `file:` source maps for Turbopack in development to avoid repeatedly embedding large `data:` source maps in server-side fake stack-frame scripts. These references must point to the emitted on-disk maps while preserving correct source resolution and symbolication through both attached debuggers and Next.js error reporting, including frames carried through nested Server and Cache rendering. Keep existing fallback behavior for source maps that cannot use an emitted file and for other bundlers.