I think we need to move the goalposts to "unrelated to/not in service of AI tooling" to escape easy mode. Replace some core unix command-line tool with something entirely vibecoded. Nightmare level: do a Linux graphics or networking driver (in either Rust or C).

Yes, I agree. The same way that when you ask "Are there any production codebases written in Language X", you typically mean "excluding the Language X compiler & tooling itself." Because of course everyone writing a tool loves bootstrapping and dogfooding, but it doesn't tell you anything about production-readiness or usefulness / fitness-for-purpose.