Wait for requested delay in rate limit errors (#2266)

Fixes: https://github.com/openai/codex/issues/2131

Response doesn't have the delay in a separate field (yet) so parse the
message.

codex-rs/core/src/error.rs

@@ -1,6 +1,7 @@
 use reqwest::StatusCode;
 use serde_json;
 use std::io;
+use std::time::Duration;
 use thiserror::Error;
 use tokio::task::JoinError;
 use uuid::Uuid;
@@ -42,8 +43,10 @@ pub enum CodexErr {
     /// handshake has succeeded but **before** it finished emitting `response.completed`.
     ///
     /// The Session loop treats this as a transient error and will automatically retry the turn.
+    ///
+    /// Optionally includes the requested delay before retrying the turn.
     #[error("stream disconnected before completion: {0}")]
-    Stream(String),
+    Stream(String, Option<Duration>),
 
     #[error("no conversation with id: {0}")]
     ConversationNotFound(Uuid),