AppKit notice in window.contentView can sit under portal overlays

In a macOS app that hosts terminal or web surfaces in portal views installed as siblings above window.contentView (in the theme frame or a glass foreground view), a transient notice label added as a subview of window.contentView is drawn below those portals and can be invisible. Install transient overlays at the same level as the portals (the app's overlay target resolver) instead. Also, NSAccessibility announcementRequested is more reliable when posted with element NSApp and a high priority than on a label that was just added to the hierarchy. And when classifying whether a key 'types text' to decide if a shortcut should run inside a text field, counting every U+F700-F8FF function-key character as non-text also lets arrows, Home/End and Forward Delete through; restrict it to F1-F35 (U+F704-F726) and treat Cmd/Ctrl chords separately.