> Lifetime analysis is a local analysis, same as any other kind of type checking

That's what the compiler is doing.

The developer (or LLM) is supposed to do the global reasoning so that what they end up writing down makes semantic sense.

Sure, throwing a bunch of variants at it and see what sticks is certainly an approach, but "lifetimes check out" only proves that the resulting code will be memory safe, not that it actually makes sense.