Hi. I have a pretty big game that I make through quest that I've thought about publishing on Steam before. Wrapping a Twine game as an .exe is pretty simple with nodewebkit, but it doesn't seem like there is an equivalent for Quest files. Any ideas on how to accomplish this? I've even thought about packaging the entirety of quest alongside the game, but I have no idea how to set it to auto-open the game file if I do that (and I imagine there would be copyright issues lol)

I don't think there is a Quest to exe function yet.
Just publish the game, and add a note that "Quest is required" and add a link to this site.

You have to ship something through steamworks, they test it. afaik they would not accept something hosted offsite like that.