Generalize retryable_upstream_status to HTTP 500-599 plus 429.
Improve execute_with_retry log label with actual status.
Preserve OpenAI InternalServerError 5xx in map_error after overload check.
Unify native stream send: log via _raise_for_status then optional async aclose.
Add _maybe_await_aclose for httpx doubles in tests.
Rename openai compat retry tests to 5xx; parameterize native/limiter/mapping tests.