(A few months later, 'cause I had to clean out enough of the garage to get the car in over the pit and buy a Warn Pullzall (110VAC comealong - got a smokin' deal on it) to pull it in, then wait for a break in the weather, since the garage is unheated...)
But now the cover's off and I've confirmed that the driver's side chain broke. Since the driver's side chain drives the passenger side chain, what sounded to me like just the crank and no cams cranking was in fact just the crank and no cams cranking. It's not clear whether the chain broke on its own, or whether it was caused by a guide fragmenting, and there are some loose plastic bits in there. Doesn't matter much, timing kit is en route from Rock.
As for whether anything got hit, jury's still out. It's so damn tight along the sides of the engine that I'm not sure I can get a compression gauge in there. But I'm also replacing the steering rack while it's over the pit, so I'll be dropping the exhaust and can take a peek up at the valves. Otherwise, I'll just see how things behave once the new kit is installed. I do have an untested junkyard motor on the shelf (bought as a spare a couple of years ago), so I can draw upon that if necessary.
But I'll see how it goes over the next few days.