2.1.5: Improve GitHub auth recovery and token failure handling

What’s changed

• Stopped automatic sign-out loops on expired GitHub sessions
• Added a manual re-auth path for GitHub session expiry
• Improved the unable_to_get_user_info message with clearer recovery guidance
• Added minimal GitHub /user failure diagnostics (status, x-github-request-id, x-ratelimit-remaining)
• Invalidated the local app session when a confirmed GitHub auth failure is detected server-side

Why

This release reduces stuck login states caused by revoked or invalid GitHub OAuth tokens, while keeping recovery explicit and minimizing token churn.

How to upgrade

Pull main and deploy 2.1.5.

Full Changelog: 2.1.4...2.1.5