Add the NSStatusItem (macOS) / Shell_NotifyIcon (Windows) tray via the
tray-icon crate: the same 5-item menu, left-click window toggle, a themed
icon (auto uses a macOS template image that adapts to the menu bar), a
static QBZ tooltip, and live icon-variant switching. tray_icon::TrayIcon is
!Send and (on macOS) must be built on the main thread with NSApplication
running, so it lives in a thread_local created via invoke_from_event_loop;
its events are drained from a slint::Timer.
macOS close-to-tray reuses the cross-platform Slint hide/show path. The
opt-in Hide Dock icon toggle switches the NSApplication activation policy to
.accessory while closed to the menu bar (.regular by default, Spotify-style)
via objc2-app-kit.
cc
vicrodh
a91d629c2b