V247 - ONE-SHOT ARBITRATION ON JOIN / LEAVE

- Arbitration uses a numeric one-shot state: 0 = idle, 1 = pending one visit.
- A real remote-player join raises the state from 0 to 1.
- A real remote-player leave raises the state from 0 to 1.
- If Arbitration is already open, the state resets to 0 immediately.
- If the host is in the world, Arbitration is opened once and the state resets to 0.
- Pressing Play resets the state to 0 before returning to normal gameplay.
- The state is not kept alive as a repeating force, preventing Arbitration loops.
- V246 slot/character cleanup rules remain unchanged.
- No CHR/BIO deletion from account storage, no backups, no auto-restore.
