Closing the main window hides it on macOS and Windows; the page and the
Host keep running and the next show resumes the same document. Windows
gets a permanent tray icon (open / quit) and a one-time notification the
first time the window is hidden after installation.
Every ordinary quit entry asks the Host over a new quit-inspection IPC
request for active tasks (same rule as the update restart check) and
armed scheduled reminders (schedule family of workspace/session-activity
for loaded sessions). Nothing to interrupt quits silently; otherwise a
native message box explains what stops, with Quit as the default and
Cancel on Esc. Inspection failure or a missed two-second deadline counts
as running tasks. The installer restart, fatal recovery, the development
restart command, and OS session end skip the confirmation.
Also: defer the downloaded-update confirmation while the window is hidden,
render the tray ICO from the vector icon, and point the installer's
running-application message at the tray.
Closes#4013
winewill
4745934683