docs: fix outdated tiebreak signature in AGENTS.md (#49)

Author: mormubis

AGENTS.md

@@ -107,7 +107,11 @@ pnpm lint && pnpm test && pnpm build
 All tiebreak functions consumed by `@echecs/tournament` must conform to:
 
 ```typescript
-(playerId: string, games: Game[], players: Map<string, Player>) => number;
+type Tiebreak = (
+  player: string,
+  rounds: CompletedRound[],
+  players: Player[],
+) => number;
 ```
 
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