The power out wire for the alternator somehow ended up touching the exhaust manifold which caused the insulation to melt and then short out. Which then caused the main power wire for all the auxiliaries, lights, ignition, etc to short all the way to the starter. So both wires need replacing, but the rest of the electrical system seems ok since those wires are pretty isolated from everything else. The car is all nice and safe in my garage but I probably won’t get around to fixing it until the weekend at least.
Also I just realized this is the second time the car has tried to self immolate itself. Both times required the use of a fire extinguisher but this time was arguably smaller.