Disabling and reenabling decorations disables fullsize_content_view

Description

When a window is created with .with_fullsize_content_view(true), calling window.set_decorations(false) followed by window.set_decorations(true) disables the fullsize content view setting, so the titlebar now appears outside the window.

I was hoping to use WindowEvent::{CursorEntered,CursorLeft} to enable the titlebar when the cursor is in the window, but this only works with a fullsize content view, since otherwise the titlebar is outside of the window, so cursor left fires when you move the cursor to the title bar, so you can't click it.

I suspect that what I actually want is something other than window.set_decorations(false), since that also disables the rounded corners of the window, and I just want to hide and unhide the title bar dynamically.

macOS version

ProductName:		macOS
ProductVersion:		15.6.1
BuildVersion:		24G90

Winit version

0.30.5

Start by reproducing the macOS sequence with .with_fullsize_content_view(true), then call set_decorations(false) and set_decorations(true) while observing the resulting titlebar and content view. Trace the macOS window handling for these APIs; done means the fullsize content view remains enabled, or the supported way to hide and restore only the titlebar is documented or exposed.