- Mark Codex usage limit errors as credential-scoped across HTTP and WebSocket executors.
- Support both top-level and nested error structures with case-insensitive matching when parsing retry-after resets.
- Propagate prevalidated candidate context to session affinity and built-in selectors during auth selection.
Closes: #5529
- Added `isCodexUsageLimitError` to detect and handle `usage_limit_reached` errors from Codex responses.
- Updated `newCodexStatusErr` to treat usage limit errors as HTTP 429 with proper `RetryAfter` handling.
- Enhanced test coverage to validate usage limit error handling, including reset time parsing and retry behavior.
Closes: #2886