A 28-year-old male construction worker is brought to the emergency department 45 minutes after a fall from a 12-foot scaffold onto concrete. On arrival, he is confused and combative. Vital signs: BP 145/92 mmHg, HR 102/min, RR 24/min, SpO₂ 94% on room air. Physical examination reveals a 4 cm laceration over the left temporal region with mild CSF rhinorrhea. Pupils are equal and reactive. Neurological assessment: opens eyes to pain (E2), makes incomprehensible sounds (V2), localizes to pain (M5). CT head shows a left acute subdural hematoma (3 mm thickness) with 2 mm midline shift, no brainstem involvement. What is the most appropriate next step in management?