fix(server): mark games abandoned on room teardown + staging leaderboard

When handle_player_leave emptied a room or handle_end_game was invoked,
the room was removed from memory without touching games_v2. Periodic
cleanup only scans in-memory rooms, so those rows were stranded as
status='active' forever — staging had 42 orphans accumulated over 5h.

- event_store.update_game_abandoned: guarded UPDATE (status='active' only)
- GameLogger.log_game_abandoned{,_async}: fire-and-forget wrapper
- handle_end_game + handle_player_leave: flip status before remove_room
- LEADERBOARD_INCLUDE_TEST_DEFAULT: env override so staging can show
  soak-harness accounts by default; prod keeps them hidden

Verified on staging: 42 orphans swept on restart, soak accounts now
visible on /api/stats/leaderboard (rank 1-4).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/stores/event_store.py

@@ -432,6 +432,23 @@ class EventStore:
                 winner_id,
             )
 
+    async def update_game_abandoned(self, game_id: str) -> None:
+        """
+        Mark a game as abandoned — used when a room empties before the game
+        reaches GAME_OVER, so games_v2 never leaks as stranded 'active'.
+        Only flips rows that are still active so a legitimately completed game
+        never gets reverted.
+        """
+        async with self.pool.acquire() as conn:
+            await conn.execute(
+                """
+                UPDATE games_v2
+                SET status = 'abandoned', completed_at = NOW()
+                WHERE id = $1 AND status = 'active'
+                """,
+                game_id,
+            )
+
     async def get_active_games(self) -> list[dict]:
         """
         Get all active games for recovery on server restart.