feat: improve error message for failed structuredClone calls #140
Description
await conversation.external(() => () => 0)throws a confusing error.
It throws an error because the function passed to external returns a function. That is a return value that cannot be cloned, which is why structuredClone errors out. The code also is incorrect because the function cannot be serialised.
We should catch the error and throw a new error with a more helpful error message. It should include the original error as its cause.