Stable, Mutable References

Carbon seems interested in taking cues from Ante for it’s future memory safety story https://github.com/carbon-language/carbon-lang/pull/5914/files#diff-10e921a79c42aea1ba84ebc626095e7e40c99acf021e90ab6f0fbce8ca1b2c71R187

This is very cool work that I automatically don’t quite believe! :-D But it seems pretty thorough, I can’t think of any counter-examples. I’ll have to keep pondering it.