Thin connectrpc client over the generated
[polyc_proto::proto::polychrome::agent::v1::AgentServiceClient].
Both the operator CLI (polychrome send) and the reference-edge receiver dial the
external-facing AgentService with the same durable-receive dance: send
one [AgentRequest], obtain its receipt, then drain the attached
AgentResponse
stream, and render each non-empty content block to user-visible text. This
crate is the single home for that logic so the two call sites can't drift.
RPC-client concerns deliberately live here rather than in
polyc-agent (the turn-loop crate, the wrong layer for a transport
client).
Buffered and incremental response projections build on the same receipt and attachment client.