The heat is from compression, not friction. And besides that, this thing is only flying at mach 1.5, there are TONS of aircraft that fly at those speeds (and much faster) with windshields.

The reason it doesn’t have a front windshield is because the change in shape of the aircraft at the windshield, to be more vertical, was disrupting their method of reducing the sonic boom. The aircraft needs the shape it has, so a windshield would have to be like 20 feet long to offer any forward visibility.