A 6-year-old girl from rural Maharashtra presents with recurrent episodes of vomiting, lethargy, and behavioral changes over 2 months. Serum ammonia is 120 µmol/L. Plasma amino acid analysis shows elevated glutamine and alanine; citrulline is low. Urine orotic acid is normal. Genetic testing reveals argininosuccinate lyase (ASL) deficiency. She is currently on a standard diet with normal protein intake. What is the most appropriate next step in management?