Closing the window now runs a graceful exit (so trackers get their
terminal scrobble), but the teardown kept the window on screen for
seconds while screens visibly emptied as servers disconnected.
Hide the window as the first step of exit teardown, bounded so a
stalled platform channel cannot hold an already-accepted exit open, and
cover every graceful-exit entry (window X, Cmd+Q, OS-initiated), not
just the close button. Add a terminal MultiServerManager.shutdown() that
closes the status streams before draining clients: the still-mounted
widget tree must never observe an "all servers gone" snapshot mid-exit,
which would flip the app into offline UI and dismantle screens (and
with it the teardown-driven AppLifecycleListener used-after-dispose
assert). A health result landing after shutdown is a silent no-op.
Supersedes the flag-based approach in #1999.
edde746
436fd7d2d5