Thanks. India (ordinarily at least) doesn't require a transit visa if you don't leave the transit area and your connection is less than 24 hours. I have an email in to the Indian Embassy here to confirm that is still the case.

This leads to the next issue of luggage. If Uzbek Air can't interline our bags to Singapore, then we'll have about 8 hours to figure out how to deal with that before our connecting flight. Worst case, we have to leave our checked bags in Delhi. It's only stuff, I guess. I'd hate to lose the really sweet handmade kitchen knife we bought in Bukhara, but probably best not to try and carry that on.