V313 — PLAYER 1 QUITS PARTY: ALL CLIENTS RETURN TO MAIN UI

BASE: V312, with only multiplayer UI additions.

GOAL
When the actual multiplayer host (Player 1) quits a party, clients who
had joined that party should automatically return to BG2's START/main UI.
The host's native Quit Party action already returns to main; V313 adds the
CLIENT-SIDE check after the host leaves or the joined session disconnects.

HOW IT WORKS
- A client is armed only after it enters a real multiplayer session with
  a populated Player 1 row. Joining errors prior to entering a game remain visible.
- When BG2 reports that player 1 has departed, or the client loses the session,
  the UI dismisses the session-end dialogs and returns to the main screen.
- A player 2/3/4/5/6 departure alone does not trigger the automatic main-menu return.
- Account login remains active. Main-menu Exit/cross-window Exit still work as before.
- Does not modify character Import/Export, router, account storage, LAN, or the
  native engine's actual disconnect sequence.

INSTALL
1. Close all BG2 instances.
2. Extract this V313 ZIP.
3. Run SETUP_IN_GAME_ACCOUNTS.bat (same setup entry point as V312).
4. Start BG2 normally via BaldurII.exe and host/join as usual.
5. Have Player 2 enter the party. Player 1 quits the party.
6. Verify Player 2 reaches the START/main UI automatically without pressing Quit.

LIMITATION
The change relies on BG2's UI callbacks and detectable multiplayer session state.
Actual host-disconnect timing and engine-generated system popups require testing
in a real Windows BG2 LAN session. If a native modal escapes UI.MENU interception,
record a screenshot and the screen you were on.

NO AUTOMATIC CHARACTER BACKUPS OR MODIFICATIONS ARE ADDED BY V313.
