V240 - STRICT ACCOUNT CHARACTER ACCESS + LOCALHOST JOIN + PERSISTENT ACCOUNT BINDING

ACCOUNT CHARACTER ACCESS POLICY
1. Plain shared `characters` backing directory = denied/parked while an account is logged in.
2. `characters_<any other account>` = not exposed to BG2 for the logged account.
3. Only `characters_<logged account>` is readable/importable/exportable.
4. The router exposes that one allowed account through `readable_characters_<logged account>`.
5. BG2 still requires its literal engine path named `characters`, so while logged in that path is only an engine alias to the one allowed readable view. It is never a fallback to the old shared folder.
6. No CHR/BIO file is copied, backed up, restored, or duplicated by this routing.

MULTIPLAYER
- Account-bound slot ownership persists after a player disconnects.
- Account-bound character ownership metadata persists after disconnect.
- The departed live/session character is removed from the multiplayer session.
- The host is forced back to the Arbitration screen when a player leaves, and removal is processed there.
- Reconnecting with the same account reclaims the same reserved slot.
- A joining account is reduced to one live character-control slot; unreserved empty extra slots are returned to the host.
- Locked multiplayer account names remain bound to the logged-in account.

DIRECT IP
- Join Game defaults to 127.0.0.1.
- The IP field remains editable if a different host IP is needed.

NO BACKUPS
- No automatic character backup, restore copy, or respawn behavior is added.
