A 52-year-old man from Delhi presents with a 3-month history of progressive left-sided weakness and sensory loss in a pyramidal distribution. MRI brain shows a well-defined, T2-hyperintense mass in the right motor cortex with minimal surrounding edema and no enhancement on contrast-enhanced T1. Diffusion-weighted imaging shows no restricted diffusion. There is no mass effect or midline shift. What is the most likely diagnosis?