A 6-month-old female infant of consanguineous parents presents with recurrent episodes of vomiting, irritability, and developmental delay. During a febrile illness, she develops seizures and altered consciousness. Blood ammonia is 520 µmol/L. Plasma amino acid analysis shows: citrulline 45 µmol/L (normal 20–50), arginine 25 µmol/L (normal 40–130), and elevated glutamine. Urine orotic acid is normal. Urine contains high levels of argininosuccinate. What is the most likely diagnosis?