A 52-year-old woman is brought to the trauma bay 20 minutes after a motor vehicle collision. She was unrestrained and struck her head on the windshield. On arrival: BP 168/94 mmHg, HR 68/min (bradycardic), RR 28/min, SpO₂ 92% on room air. Neurological examination: eyes open to pain (E2), no verbal response (V1), extends to pain (M3). Left pupil is 5 mm and sluggish; right pupil is 3 mm and brisk. There is blood in the external auditory canal bilaterally. CT head shows a large right epidural hematoma with 8 mm midline shift and uncal herniation. What is the most appropriate immediate intervention?