macos-hidden: add an option to hide the app only when no windows are open

[dacarley]

I run Ghostty mainly for the global quick terminal (keybind = global:cmd+backquote=toggle_quick_terminal), with initial-window = false and quit-after-last-window-closed = false.

macos-hidden = always gets close, but it hides the Dock and Cmd+Tab icon even while I have regular terminal windows open, which makes those windows hard to switch to.

Request: a value such as macos-hidden = when-no-windows that hides the Dock and app switcher icon when no regular windows are open (the quick terminal doesn't count), and shows it again as soon as a normal window opens.

That would make Ghostty a quiet always-ready drop-down terminal that still behaves like a normal app when you're using full windows.