On a sharded Realm, an item every roller passed on stays locked #703

Expected (1.12.1). When every roller passes on a group-loot item, the item becomes free for anyone to loot. vmangos Group::CountTheRoll clears the roll and marks the item free when no one chose Need or Greed.

Actual (at 7f9ec8ab). On a sharded Realm, Realm-core resolves the roll. resolve_roll calls unlock_row_ffa on an all-pass (rolls.rs:568), and on a win with no eligible winner (rolls.rs:728). unlock_row_ffa (rolls.rs:623-633) updates game_corpse_loot, but Realm-core holds no corpse loot, so the call does nothing. The loot-roll Relay settles only ROLL_WON events on the World Shards (loot.rs:219-243, through settle_loot_roll at loot_roll.rs:113). No event clears withheld on the Shard that holds the corpse.

How it shows. A group passes on an item. The item stays locked in the corpse window, and no one can loot it. Once #701 merges, every roller also sees "Everyone passed" for that item.

Fix direction. Let the Relay unlock the Shard's row after an all-pass, as it settles a win now. One option: read ALL_PASSED events from Realm-core next to loot_won_since, and fan a gw_ or realm_ unlock call to each World Shard. A Shard that does not hold the corpse ignores the call, the same as with settle_loot_roll's withheld guard. Cover it in a cross-Shard durable test.