Cmd+W closes app; should hide window and allow reopen/reconnect

[jmcte]

Problem

On macOS, pressing Cmd+W closes the app completely instead of hiding the main window.

Expected

Cmd+W should hide the UI (keep the app running) and allow the user to reopen the window (e.g., via dock click or menu) with the session intact.

Steps to reproduce

1. Open CodexMonitor on macOS.
2. Press Cmd+W.
3. App exits instead of hiding the window.

Notes

A typical macOS pattern is to keep the app running and just hide/close the window; reopening should restore the UI and reconnect state if needed.