Tried one last thing before going to buy some new valves for my kitchen sink... actually probably would have anyway had I not been stuck at a job site until after 7PM. Anyway, the hot water shutoff valve to the sink was weeping, so last night I tried one last thing before condemning it. I closed it about halfway, and then let the hot water run out the faucet for about a minute or so. I figured there might be some crud on the backside of the seal that was keeping it from sealing well. Then with the faucet still open I opened the shutoff valve fully, giving it a good crank. Came home tonight, bone dry. I know that I should tighten the packing nut, but I don't know if that is even possible - they are REALLY crusty. (yes, I do know that you should exercise all valves every year or so, but PO's apparently did not.) I really didn't want to replace them because of location, so that can wait for a full kitchen renovation when the cabinets are out of the way.
Of course, there is now a tiny trace of water in the middle of the cabinet, and I can't see where the heck it came from, unless it came from around the faucet but so long ago that it's dry again. (still haven't replaced the faucet, as SWMBO didn't see anything she liked at the Despot, and it'll be Saturday before we can go to the real plumbing store together.)
Also found out that the air gap for the dishwasher used to be required by code here, but no longer is, and a sink replacement still falls under a "fixture replacement" so I don't need to pull a permit even if we do replace the sink. (My job requires me to maintain decent relations with various code officials, so I either have to "do it right" or make sure nobody ever finds out...)
nate