Well I took it into them and they discovered that the rear bushing on the front passenger side control arm is shot. The whole arm is a $70 part on rockauto and looks like a pretty straightforward bolt in which I intend to do myself. They said they couldn't realign it til that issue was resolved, but that they'd realign it for free when it is. I'm still struck by the fact that the car behaved just fine until I brought it to them. I've never seen an alignment machine, but does it seem like this is something they could have caused while aligning it? There's no obvious trauma to anything else under there.