fix: handle macos fullscreen close

[ritteralvaro]

Summary

Fixes a macOS native fullscreen window-management issue when closing Ferdium while "Keep Ferdium in background when closing the window" is enabled.

When the main window is in native fullscreen, Ferdium now waits for the leave-full-screen event before hiding the window.

Details

The previous logic registered a show listener that re-entered fullscreen after the window was shown again. On macOS this can cause an odd hide/reopen loop or window-management glitch.

This change removes that re-enter-fullscreen hook and keeps the existing Windows behavior unchanged.

Testing

• Tested locally on macOS.
• Entered native fullscreen.
• Pressed Cmd+W.
• Confirmed Ferdium exits fullscreen and hides cleanly.
• Ran project hooks during commit: typecheck, lint/format, and tests passed.

Fixes #2442