Add optional @openai/codex-sdk exec-backed runner mode behind CODEX_RUNTIME=sdk, with CODEX_RUNTIME_SDK_ROLES canary limiting and app-server fallback for unsupported flows.
Add optional @openai/codex-sdk exec-backed runner mode behind CODEX_RUNTIME=sdk, with CODEX_RUNTIME_SDK_ROLES canary limiting and app-server fallback for unsupported flows.