th.sort {
            position: relative;
            cursor: pointer;
            user-select: none;
        }
        /* 箭头盒子：垂直排列，上下分开，中间留空隙 */
        th.sort .arrow-wrap {
            position: absolute;
            right: 10px;
            top: 50%;
            transform: translateY(-50%);
            display: flex;
            flex-direction: column;
            gap: 4px; /* 上下箭头中间间隙 */
        }
        /* 上三角样式 */
        .arrow-up {
            width: 0;
            height: 0;
            border-left: 7px solid transparent;
            border-right: 7px solid transparent;
            border-bottom: 8px solid #ccc;
        }
        /* 下三角样式 */
        .arrow-down {
            width: 0;
            height: 0;
            border-left: 7px solid transparent;
            border-right: 7px solid transparent;
            border-top: 8px solid #ccc;
        }
        /* 升序：上三角变黑 */
        th.sort.asc .arrow-up {
            border-bottom-color: #222;
        }
        /* 降序：下三角变黑 */
        th.sort.desc .arrow-down {
            border-top-color: #222;
        }