pw::FunctionRef is a non-owning reference to a callable object. It provides similar functionality to C++26 std::function_ref.
Unlike pw::Function, it does not hold ownership of the callable or its context. It is intended for use as a synchronous callback parameter where the callable is guaranteed to outlive the function call.
pw::FunctionRef is not nullable and must be initialized with a valid callable object. This matches the semantics of C++26 std::function_ref.
Example: