Well, shoot.
Keying off longer and doing a secondary key-off during a glide doesn't always work. In fact, not at all for a couple days. Then today it did idle back down after bump starting.
I've done several engine-on coasts up to a stop light. It idles high all the way to the light and then goes down after sitting at the light for about seven seconds. After ten seconds, it's idling around 700 like it ought to. Some crazy VSS logic?
I've heard of automatics holding a higher idle when coasting in neutral (a Saturn, IIRC), but Olivia's a manual.