feat: iterate on pipe to shell

[cablehead]

I'm still not sure what the end picture looks like, but there's obvious improvements to the status quo:

• see the source clip as well as the command / output
• change run command to "shift-enter", which doesn't put the output in your stack, but it does capture the command (to be used for command completion later).
• CMD-Enter "captures" the output
• ie. puts it at the top of your stack, on your clipboard and closes the Stacks window.

Stretch, given this is an iteration: fuzzy auto-complete previously captured commands