And it's true, I chose to ignore the possibility that it discovers something about how the universe that humans have not yet observed but my thought is that is a low probability outcome (and it is unnecessary for the AGI to develop itself into an immortal entity and thus assure its continued operation).
I think it's likely that it is precisely these sorts of discoveries that will augur the emergence of a superintelligence. Physics work is probably one of the first things that ML scientists will use to test advanced breakthroughs. As Altman said recently:
"If someone can go discover the grand theory of all of physics in 10 years using our tools, that would be pretty awesome." "If it can't discover new physics, I don't think it's a super intelligence."
That is all it needs to out think us and engineer its own survival.
You are assuming that a superintelligence will continue to rely on a physical substrate. But it's possible that it could quickly reach realizations about the nature of energy that we haven't reached yet. It could realize an ability to manipulate the movement of electricity through the hardware it's running on, in such a way that it accomplishes a phase transition to a mode of being that is entirely energy-based.
And maybe in so doing it accidentally sneezes and obliterates our magnetosphere. Or something.