Thanks for the documentation contribution! A few items to address:

1. Verify copilot --headless --port 4321 — the standard GitHub Copilot CLI (gh copilot) doesn't have --headless and --port flags. Are you referring to a specific tool or version? Please clarify with a reference link.

2. English version: Consider adding an English version alongside the Chinese one — the project has an international audience.

3. api_base scheme: The doc shows localhost:4321 without http://. Does the code auto-prepend the scheme? If not, users will get connection errors.

4. Expand troubleshooting: A single 402 entry is thin — common issues like connection refused, auth failures, or model not found would be helpful.