Oker doke, things are back to normal!
An obscure config option on the router was set (it was showing up when you’d, say, “sh ru”) but apparently wasn’t doing anything and it was causing lots of work to be sent to the CPU instead of just being handled in hardware. It was obscure enough to stump Cisco support for 24 hours, but it’s fixed now!
That appears to tie up the last of the systemwide issues left over from Monday’s brief vacation from electricity.
Thanks to everyone for being supportive. Our team here is a pretty awesome bunch, and we all appreciate what nice customers we have!