BookNest's checkout from Navigation was a placeholder behind the Stack.Protected guard. A real one rejects bad input before it leaves the phone and copes when the server refuses a valid order. This section builds it with React Hook Form 351,018 (7.88.0) for the fields, Zod 44,027 (4.6.5) for the rules, and @hookform/resolvers (5.9.1) between them, all plain JavaScript with no native rebuild.