Refresh ChatGPT auth token (#2484)

ChatGPT token's live for only 1 hour. If the session is longer we don't
refresh the token. We should get the expiry timestamp and attempt to
refresh before it.

codex-rs/core/src/client.rs

@@ -252,6 +252,14 @@ impl ModelClient {
                         .and_then(|v| v.to_str().ok())
                         .and_then(|s| s.parse::<u64>().ok());
 
+                    if status == StatusCode::UNAUTHORIZED {
+                        if let Some(a) = auth.as_ref() {
+                            let _ = a.refresh_token().await;
+                        }
+                        // Retry immediately with refreshed credentials.
+                        continue;
+                    }
+
                     // The OpenAI Responses endpoint returns structured JSON bodies even for 4xx/5xx
                     // errors. When we bubble early with only the HTTP status the caller sees an opaque
                     // "unexpected status 400 Bad Request" which makes debugging nearly impossible.