[Beta v3 PvP] Win jingle and win screen fire multiple times at match end

**Status: root cause confirmed**
**Affects:** MultiplayerPvP Closed Beta v3 (mqtt branch)

## Symptom
Tester reports: "the winning sound plays like 3x" / win screen re-triggers at match end.

## Root cause
The Lua referee port dropped the legacy TS server's game-over guard. `try_resolve_round` (`pvp_api/referee.lua:154-191`) runs on every `play_hand` the host receives — both players, including the host's own loopback, plus stray sends near match end (`play_hand(chips,0)` at `ui/game/game_state.lua:304`, `play_hand(0,0)` on deck-out at `game_state.lua:454`). Once a player's lives hit 0, `lives_blocker` stops further life loss, but the `broadcast("pvp_win", ...)` at `referee.lua:183` re-fires unconditionally on every subsequent resolution attempt — and the same missing guard applies to the other `pvp_win` broadcast sites (`referee.lua:241, 268-274, 287, 299`).

Each duplicate `pvp_win` loops back through `action_win_game`/`action_lose_game` (`networking/action_handlers.lua:465-476`), which have no idempotency check, replaying the jingle and screen each time.

Related (unconfirmed, likely same class): the forfeit path `pvp_player_won` (`pvp_api/gamemodes.lua`) and practice-mode win paths (`lib/ghost_replay.lua`) are structurally similar and may exhibit the same symptom.