Also, the ball has been in Typescript's court for a while to provide a fast, easy to use typecheck-only API that receives an AST and can be used by other tools

Also, the ball has been in Typescript's court for a while to provide a fast, easy to use typecheck-only API that receives an AST and can be used by other tools that already have parsers. If that existed, it would allow Typescript it to be embeddable, and Rome could use that. People have been asking for it for half a decade.