[drdeca]

Seems implausible. The fusion presumably wouldn’t keep going if it breached the walls.

Also, to be bright enough that we would see it from here as a star, I imagine it would require enough material that one might as well just let gravity do the job rather that use a Tokamak?

Maybe there are efficiency gains that are large enough that it wouldn’t actually require as much material as a star? I wouldn’t guess so though.