The belt was completely fragged, cracking and peeling. I'm just surprised it didn't die earlier.
Checked all the pulleys, idlers, and the water pump. All turned freely. Turned it over a few times with the covers off, and everything moved, no squeaks or grumbles.
Checked the alignment after turning it over a few times, and it seemed spot on still. As for the compression check... not easily. I'd need to buy or scare up a gauge.
The car ran fine right up to the driveway, and just wouldn't start the next day.
It's actually my friends' car, and they had a mechanic look at it (who apparently snapped off one of the left cover mount bolts. idiot) before I came over to do the belt replacement. I sure hope they didn't dink around with anything else.