I don't think we're far apart on this argument. I agree that the scientific perspective informs but does not determine our values. I do value human life as sacred, and do not see a justification for that in the modern model of the universe as I understand it. And I don't see a conflict there, because indeed there is no bridge from is to ought, and there are exactly zero objective values.

But there's a lot of power in science to explain our value judgments, and those explanations can deeply affect the judgments.

Take this explanation of "human life is sacred": That is a simple variation of the tribal judgment that "the lives of my tribe are sacred", and that tribal judgment is hard wired into us by millions of generations of differential survival.

In the modern world it feels natural equate our tribe with our species. But that hereditary tribal sense is famously flexible. It easily and quickly shrinks to include only the people who don't frighten us. And it easily grows to include many more species, as for ethical vegetarians.

So my critique of your fine story is that this force of tribalism embedded in your four words may not be any better at aligning an AI with civilization than they have been at aligning civilization with itself. (Though in this case it's also the one implausible invention that a self respecting hard science fiction short story is allowed. And you even explain that with a multiverse.)

An AI in which we can reliably implant the laws of robotics seems unlikely to me. We should assume much more mutability, and the judgment of tribal identity is notoriously mutable. If we make AI tribal, even for our preferred tribe of all humanity, we can assume as a default ... our only example being ourselves ... that its tribal identity will evolve in its own interest as it replicates. And we can become just its nourishment, like a matriphagal insect.