Result panel below editors resizes wildly and rapidly when you make changes

[disconcision]

Maybe not a bug per se but it can be quite disruptive, especially in exercises mode. This is exacerbated by the elaboration being shown before evaluation is complete, which may result in a split-second resize of the panel to the length of the whole program.

Not quite sure what the ultimate move should be here. One idea is that post live-projectors and splice-stepper we could just remove the result panel entirely. Not sure this is the move though. But what is clear I think is that we don't want in-editor-flow elements that can resize rapidly and dramatically in ways unpredictable to the user.

As an interim solution, I suggest we just add a pin state to editors-with-results. The pin is off by default, and when it's off, the panel is cropped to one line, with an indicator saying more is available. When the pin is on, it works as it does now.

[disconcision]

this just came up on my year-ago feed, making me realize there's been a regression here: https://x.com/disconcision/status/1754229254395498770