- Add `PayloadFinalizer` to apply configuration rules at the final serialization barrier
- Support decoding, modifying, and re-encoding Devin protobuf business fields
- Add multipart form-data payload normalization to JSON for media payload rules
Closes: #5067
- Implement `streamCodexDuplex` to handle bidirectional WebSocket interactions for Codex
- Support steering continuations (`response.steer`) and queued creations (`response.create`, `response.append`)
- Preserve response settings and state transitions across steering updates and automatic successors
- Isolate connection-level failures with `codexDuplexConnectionError` to prevent unnecessary credential cooldowns
Closes: #5968