The default launch mode stacked a second MainActivity — with a second
ViewModel, session and CallManager — whenever the app was re-entered.
The visible screen's Hang up then commanded a manager with no call while
the real call rang on underneath, and the peer never got the END.
singleTask, plus a 30s connect guard so an answered call whose ICE never
finds a path gives up out loud on both screens instead of sitting in
Connecting forever.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
