Policy: leaving a match after accepting (two-tier consequences)

**Status: needs triage** (policy / enhancement)

## Summary
Once a player accepts a match (Balatro-Multiplayer/BalatroMultiplayer#493), they may still need to leave. Consequences should depend on **when**:

- **Leaving after the run has started** → treated as a **normal loss** (full game loss + MMR loss), same as any forfeit mid-game.
- **Leaving during the ban phase** (before the run starts) → **some MMR loss but no game loss**, plus possibly a **queue-time penalty**. Bailing during bans is lighter than abandoning a live game, but shouldn't be free.

## Open questions
- How much MMR the ban-phase leave costs (fixed amount vs fraction of a loss).
- Size of the queue-time penalty, and whether it escalates on repeat.
- Exact boundary for "run started" (first blind? deck locked in?).

Start by reading the referenced match-acceptance issue, Balatro-Multiplayer/BalatroMultiplayer#493, and trace how leaving is currently handled after acceptance. No files, tests, or entry points are named here. Done requires agreement on the run-start boundary, ban-phase MMR loss, and queue-time penalty before implementation can be scoped.

Scritto dal modello di indicizzazione a partire dal testo della issue.