Streaming RPC - Incorrect Protocol impl

[AThilenius]

The streaming RPC protocol is incorrectly implemented, resulting in error responses from the connect-es client. As it turns out, the connect protocol reference is ambiguous in the spec definition of half-duplex streams. After some clarification from the Buf folks, it seems my interpretation of the spec was incorrect. Half-duplex streams are still treated as BiDi streams at the protocol level. Which unfortunately leaves a ton of ambiguity in the implementation of them. C'est la vie.