fix: Q returns to lobby instead of killing SSH session

Pressing Q in game now cleans up the session and returns to lobby,
instead of calling tea.Quit which terminates the SSH connection and
shows "Connection lost" on web. Only Ctrl+C force-quits now.

Also cleans up room on exit so abandoned rooms don't persist in lobby.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/model.go

@@ -94,6 +94,10 @@ func isQuit(key tea.KeyMsg) bool {
 	return isKey(key, "q", "ctrl+c") || key.Type == tea.KeyCtrlC
 }
 
+func isForceQuit(key tea.KeyMsg) bool {
+	return isKey(key, "ctrl+c") || key.Type == tea.KeyCtrlC
+}
+
 func isUp(key tea.KeyMsg) bool {
 	return isKey(key, "up") || key.Type == tea.KeyUp
 }