wrap the bulb in aluminum foil, what would happen? I'm guessing it could explode, setting my ininsured quadruplex apartment ablaze, but what sort of ventilation does the bulb itself need? How hot can a bulb enclosure get?

Assuming its a 400w bulb or suchlike, they are designed for "passive cooling" ie most bulb enclosures use just convection to cool the bulb. So they are designed to get very hot.

I think the bulb would probably crack at a certain point, and since it's under high pressure, it would indeed explode. As some do at the end of their life anyway.