Ugh. I made some work for myself.
The utility sink has been dripping and, since I was planning on a quick trip to Home Depot, I decided to take the faucet apart so that I could grab the right replacement parts. In removing the faucet, one of the (old) captive nuts on the copper supply line snapped.
Easiest way forward is to just cut those supply lines short, pop on some new fittings and replace the faucet altogether. Unfortunately, whoever did the plumbing didn't put any shut-offs on this run, so I've gotta shut the water off for the whole house.
Oy. ******g old houses. That'll teach me to be ambitious.