add optional in_reply_to field on send for conversation threading

hive-ag3nt/src/plugins.rs

@@ -176,6 +176,7 @@ async fn notify(socket: &Path, to: &str, body: String) {
     let req = hive_sh4re::AgentRequest::Send {
         to: to.to_owned(),
         body,
+        in_reply_to: None,
     };
     if let Err(e) = client::request::<_, hive_sh4re::AgentResponse>(socket, &req).await {
         tracing::warn!(error = ?e, "failed to notify {to} of plugin install failure");