/* ===== Canva风格四栏布局 ===== */
.design-layout {
    display: flex;
    align-items: stretch;
    gap: var(--panel-border-spacing, 4px);
    border-radius: var(--panel-border-radius, 8px);
    overflow: hidden;
    box-shadow: 0 2px 12px rgba(0,0,0,0.08);
    background: var(--panel-bg, #fff);
    /* CSS 变量 - 由系统设置动态控制 */
    --panel-border-color: #dee2e6;
    --panel-border-width: 2px;
    --panel-border-radius: 8px;
    --panel-border-spacing: 4px;
    /* 四栏宽度使用百分比，便于不同屏幕尺寸自适应 */
    --sidebar-width: 18%;
    --param-panel-width: 24%;
    --result-panel-width: 48%;
    --history-panel-width: 10%;
    --footer-height: 40px;
    --footer-spacing: 4px;
    --panel-bg: #ffffff;
    --panel-text: #212529;
    --panel-text-muted: #6c757d;
}

/* 功能区域独立边框 */
.panel-border {
    border: var(--panel-border-width, 2px) solid var(--panel-border-color, #dee2e6);
    border-radius: var(--panel-border-radius, 8px);
    background: var(--panel-bg, #fff);
    height: 100%;
    box-sizing: border-box;
    display: flex;
    flex-direction: column;
}

/* 参数面板 - 默认显示 */
.design-param-panel {
    width: var(--param-panel-width, 280px);
    min-width: var(--param-panel-width, 280px);
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

/* 历史记录 - 稍窄 */
.design-history-panel {
    width: var(--history-panel-width, 180px);
    min-width: var(--history-panel-width, 180px);
    height: 100%;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

/* 侧边栏内的历史记录 - 宽度100% */
.design-sidebar .design-history-panel {
    width: 100%;
    min-width: 100%;
}

/* 生成结果 - 占据剩余空间 */
.design-result-panel {
    flex: 0 1 var(--result-panel-width, 48%);
    width: var(--result-panel-width, 48%);
    min-width: 0;
    height: 100%;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    position: relative;
}