Type Alias EntrypointFn 

pub type EntrypointFn = dyn Fn(Value) -> Pin<Box<dyn Future<Output = Result<Value, SynapticError>> + Send>> + Send + Sync;

An entrypoint wrapping an async function as a runnable workflow.

The invoke_fn field is a type-erased async function (Value -> Result<Value, SynapticError>). Type alias for the async entrypoint function signature.