Improve artifacts

[benjaminshafii]

Artifacts are a bit buggy right now. They were supposed to represent executable files. But I don't think they bring much value.

Let's get rid of artifacts and keep "context" as the primitives to show which files we touched.

Get rid of "artifacts" and make it possible to "reveal" artifacts on linux/windows #74 (right now only tested on mac, reported issue on windows, and unknown state on linux)

This small UI should disappear for now it doesn't bring any value

Move this sidebar to the right side bar so it looks a bit closer to the claude cowork layout

[benjaminshafii]

#180