maxRecentUserMessages配置项可能有bug。设置了该值后，可能不能正常使用

涉及文件：packages/agent-core/src/agent/compaction/strategy.ts
涉及方法：DefaultCompactionStrategy

问题代码：

    for (; recentMessages < messages.length; recentMessages++) {
      const splitIndex = messages.length - recentMessages - 1;
      const m2 = messages[messages.length - recentMessages]!;

      if (m2.role === 'user') {
        recentUserMessages++;            
      }
      recentSize += estimateTokensForMessage(m2);

      if (canSplitAfter(messages, splitIndex)) {
        bestN = splitIndex + 1;          
      }

      const reachesMax = recentMessages >= this.config.maxRecentMessages
        || recentUserMessages >= this.config.maxRecentUserMessages  
        || recentSize >= this.maxSize * this.config.maxRecentSizeRatio;
      if (reachesMax && bestN !== undefined) {
        break;
      }
    }

复现过程：用消息序列 [asst_tc, tool, tool, user, user, user] 遍历时的过程：

问题：第 3 轮时 recentUserMessages 已经是 3，却错误返回了值
原因：不知道是什么问题导致，但是看起来没有什么实际影响

Start in packages/agent-core/src/agent/compaction/strategy.ts and inspect DefaultCompactionStrategy, especially the loop and maxRecentUserMessages condition. Reproduce the behavior with [asst_tc, tool, tool, user, user, user], then determine the intended split boundary and whether the returned value is valid. Done means the expected behavior is documented and covered by a regression test.