RawInvocation

A single raw invocation: resolved rpc name + per-param-list raw arguments + call metadata. args is nested (List[List[Raw]]) so each inner list is one parameter list, aligning with the per-param-list arity shape consumed by later derivation.

Raw is a fully abstract type parameter: it IS the opaque serialized-value carrier, with no transport or format API leaking into the raw layer. No concrete or opaque carrier type exists.