Fix: [兼容性问题] ChatGPT 更新 Apps/Plugins 后，Plus 账号无法重新创建 CodexPro MCP 连接

[MayVerse4]

Autonomously generated fix for issue.

Note: The agent reached its maximum cost limit ($0.51) before explicitly passing code review.

Fixes #65

[rebel0789]

This compatibility idea needs current evidence before merge. Issue #65 was already addressed in PR #66 with codexpro connection-test, request-arrival logging, and updated Plugins setup guidance; the reported browser failure occurred before an MCP initialize request reached CodexPro.

Please update this PR with:

1. A current reproduction showing that ChatGPT connector creation now requires a sessionless GET or HEAD probe, using current main and the current Plugins flow.
2. HTTP smoke coverage for GET and HEAD with and without the configured token.
3. Proof that HEAD returns no body, DELETE session behavior is unchanged, and an authenticated server does not expose metadata without valid authentication.
4. A rebase onto current main and a green Ubuntu/Windows CI matrix.

If that evidence confirms the probe is required, the change is reasonable and can be credited and merged. Leaving the PR open for those updates.