A 32-year-old man is brought to the trauma centre 2 hours after a motor vehicle collision with severe head impact. He was initially conscious but rapidly deteriorated. On examination, he is comatose with a dilated right pupil and left hemiparesis. CT head (non-contrast) shows a lens-shaped hyperdense collection in the right frontoparietal region that does not cross the midline. The collection is bounded by the inner table of the skull and does not follow the brain contour. What is the most likely diagnosis?