When I got back, my already-slightly-weak battery had finished dying.
Luckily, I was about fifty feet from a gas station. Unluckily, they didn't have a charger that they were confident would charge (but not harm) a motorcycle battery. We wound up trying a too-conservative setting on the charger, which failed to give it enough juice to start the bike. Then we tried jumpstarting the bike directly, which did no good and drained the battery absolutely dead.
So I wound up taking a cab home, charging the battery at home, and bringing it back this morning. Thanks for the ride, bk2w! And we discovered that the battery charger he uses for his Corvette has a weak setting, barely stronger than the one on my drip-charger, and a 15-amp setting which is three times the rated maximum for my battery. So I'm gonna have to be careful to never charge a motorcycle battery on that charger's default setting.
Anyway -- got back and did battery stuff just fine, and I *am*, at least, getting much faster at taking the battery out and putting it back in.