So the scarf is done.
Not as I would have liked, with colors and all intact, but patchwork-looking where the heat-setting did (or did not) work. It doesn’t look completely awful, but I don’t think it looks good.
Still, it was a learning experience, and so whenever the weather cooperates and I have time (the two are unlikely to happen simultaneously for a while) I will re-create this pattern. I know what I did that I like, and what I did that I don’t, and how to fix the second without removing the former.
Meantime, the scarf is on its way to the owner. Let’s call it a “proof of concept” mock-up of the real scarf, to be delivered at a later date.