Restore global Shell status feedback

[VolkerChristian]

Summary

• rebuild the bottom status line as a global footer with CodexUI, AISuite, and SNode.C attribution links
• show only global Ready, Attention required, Reconnecting, and Offline state; remove thread-specific and duplicated transport content
• auto-dismiss warning notices after 6 seconds and error notices after 10 seconds while preserving manual dismissal

Validation

• status-line layout visually validated
• warning/error auto-dismiss behavior visually validated
• complete test suite passes: 7/7

No protocol, ownership, controller, cache, or duplicated-state changes.