fix(session): reset lobby when player leaves finished match

docs/UI_STYLE.md

@@ -107,9 +107,9 @@ are not MVP requirements.
   safe areas, closes on outside activation or Escape, and never contains
   primary game, lobby, observer, or result actions.
 - The settings popover shows `Выйти из игры` only for an authenticated session.
-  It opens a confirmation modal; an unfinished player match warns that it ends
-  for everyone, while observer and lobby departures explain that only this
-  browser's place is released.
+  It opens a confirmation modal; a player match, including a finished result,
+  warns that it returns everyone to the waiting lobby, while observer and
+  waiting-lobby departures explain that only this browser's place is released.
 - A compact response indicator between the connection state and gear shows a
   rounded total response time or an explicit unknown, stale, or offline state.
   Its accessible description and settings details expose `Отклик`, `Связь`,