Not sure one gives you safer typing than the other in absolute. They both have a different context/purpose. TypeScript is great for typing a code base for function calls type of APIs, whereas GraphQL is great to express types for inter-system communication (usually over HTTP).
Using GraphQL to type your in-process API would be overkilled and would require quite a bit of contortionism, and while you can share same TypeScript types between your end-points interfaces (and can be a good first step), inter-process communication is better expressed with something like GraphQL or Protobuf.
Using GraphQL to type your in-process API would be overkilled and would require quite a bit of contortionism, and while you can share same TypeScript types between your end-points interfaces (and can be a good first step), inter-process communication is better expressed with something like GraphQL or Protobuf.