Match the image OAuth test path and gateway behavior: check for a
custom user_agent credential first, fall back to codexCLIUserAgent
only when no custom UA is configured.
The testOpenAIAccountConnection function was sending requests to
chatgpt.com/backend-api/codex/responses without the required Codex CLI
identification headers, causing 401 Unauthorized for OAuth/PAT accounts.
The gateway Forward path and the compact test path both set these headers:
- Originator: codex_cli_rs
- User-Agent: codex_cli_rs/<version>
- OpenAI-Beta: responses=experimental
This patch adds the same headers to the normal (non-compact) OAuth test
path. API key accounts and other platforms are unaffected since the
headers are inside the isOAuth branch.
cat