[codex][otel] propagate user email in otel events (#5223)

include user email into otel events for proper user-level attribution in
case of workspace setup

codex-rs/core/tests/responses_headers.rs

@@ -63,6 +63,7 @@ async fn responses_stream_includes_task_type_header() {
         config.model.as_str(),
         config.model_family.slug.as_str(),
         None,
+        Some("test@test.com".to_string()),
         Some(AuthMode::ChatGPT),
         false,
         "test".to_string(),