After lunch, the shop called just as we were going out for a post-meal walk to tell me, "We put the vehicle on the test stand and it passed. No repairs are necessary." So we walked back over to the shop and collected the vehicle. The $100 was the minimum charge, but I'm not complaining that much. By going through all of the necessary state paperwork hoops (and, importantly, starting the process early so I wouldn't be in a rush), I now have the necessary smog certificate (filed electronically), and I can renew my van's registration with nearly four weeks to spare. And no actual repairs were necessary.
It's almost an anti-climax that after the $100 original test fee and another $100 at the repair-and-retest station, the actual registration fee is only $58.