@deprecated does probably do what you want here, in terms of producing type checker diagnostics for code that you want to produce diagnostics. It’s conceptually not a great fit though because nothing is actually deprecated here. This might confuse users, and means that type checker configurations would work in unintuitive ways.
There’s a longstanding idea to add something like a @typing_error decorator that would work similar to @deprecated but not carry any implications about deprecation. I included that in an early version of PEP 702 but removed it for simplicity. However, new use cases keep coming up, so now may be a good time for a new PEP proposing this idea.