A 6-month-old female infant from a consanguineous family presents with recurrent vomiting, poor growth, and developmental delay. She has an aversion to protein-containing foods. Serum ammonia is 250 µmol/L. Plasma amino acid analysis shows markedly elevated citrulline (450 µmol/L; normal: 15–45) and low arginine. Urinary orotic acid is normal. What is the most likely diagnosis?