A 42-year-old Indian male presents with a 3-month history of progressive headaches, morning vomiting, and recent onset focal seizures. MRI brain reveals a well-demarcated, heterogeneous mass in the left frontal lobe with mixed signal intensity, significant peritumoral edema, and mass effect. On histopathology, the tumor shows a mixture of cells with varying nuclear sizes, frequent mitotic figures, and areas of necrosis. Immunohistochemistry is positive for GFAP and negative for IDH1 R132H mutation. What is the most likely diagnosis?