Make sos smarter about interactive processes

[mitchellwrosen]

Right now sos doesn't deal very well with commands that read on stdin (like some stack exec my-thing at the end of a list of commands).

Somehow, these interactive processes aren't actually killed right now, so sos both leaks pids and also subsequent runs compete for input from stdin.

[mitchellwrosen]

Ah, if a process spawns a child, that child isn't killed when a job is restarted.