/* ============================ 主区域 ============================ */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    position: relative;
    min-width: 0;
    background: var(--color-bg);
}
.chat-header {
    padding: 12px 20px;
    background: color-mix(in srgb, var(--color-surface) 80%, transparent);
    backdrop-filter: saturate(180%) blur(8px);
    border-bottom: 1px solid var(--color-border);
    display: flex;
    align-items: center;
    gap: 10px;
    z-index: 20;
}
.chat-header h5 {
    margin: 0;
    font-size: 0.98rem;
    font-weight: 600;
    color: var(--color-text);
    display: flex;
    align-items: center;
    gap: 8px;
}
.chat-header h5 i,
.chat-header h5 .lucide {
    font-size: 1.15rem;
    color: var(--color-primary);
}

/* 顶栏侧边栏切换按钮 + 顶栏"新建对话"图标按钮。
   尺寸与侧边栏顶部的 .sidebar-icon-btn 对齐,保证折叠/展开两态视觉一致。
   - 移动端:.sidebar-toggle 一直显示(mobile.css 媒体查询接管)
   - 桌面端:默认隐藏,仅当 body.sidebar-collapsed 时显示 */
.sidebar-toggle,
.header-newchat-btn {
    display: none;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border: none;
    background: transparent;
    color: var(--color-text-secondary);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 1.1rem;
    transition: background var(--duration-fast) var(--ease),
        color var(--duration-fast) var(--ease);
}
.sidebar-toggle:hover,
.header-newchat-btn:hover {
    background: var(--color-surface-hover);
    color: var(--color-text);
}
body.sidebar-collapsed .sidebar-toggle,
body.sidebar-collapsed .header-newchat-btn {
    display: inline-flex;
}

/* B7 深色模式切换按钮(顶栏右侧) */
/* 顶栏右侧动作区(收藏夹 + 深色切换) */
.header-actions {
    margin-left: auto;
    display: flex;
    align-items: center;
    gap: 2px;
}
/* Phase 1b 个性化:头部当前用户昵称(渠道侧快照)。窄屏隐藏避免挤占。 */
.header-user {
    max-width: 140px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    font-size: 13px;
    color: inherit;
    opacity: 0.7;
    margin-right: 6px;
}
@media (max-width: 640px) {
    .header-user { display: none; }
}
/* C 端匿名:头部「登录」入口。复用主题色,小巧不抢视觉。 */
.header-login-btn {
    display: inline-flex;
    align-items: center;
    padding: 4px 12px;
    margin-right: 6px;
    font-size: 13px;
    border-radius: 14px;
    color: var(--color-primary, #2f6bff);
    border: 1px solid var(--color-primary, #2f6bff);
    text-decoration: none;
    white-space: nowrap;
}
.header-login-btn:hover { opacity: 0.85; }
.theme-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border: none;
    background: transparent;
    color: var(--color-text-secondary);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 1.2rem;
    transition: background var(--duration-fast) var(--ease);
}
.theme-toggle:hover {
    background: var(--color-surface-hover);
}
#favEntry.is-active,
#favEntry:hover {
    color: var(--color-primary);
}

/* 移动端遮罩 */
.sidebar-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(15, 15, 25, 0.4);
    z-index: 90;
    opacity: 0;
    transition: opacity var(--duration-base) var(--ease);
}
.sidebar-backdrop.visible {
    display: block;
    opacity: 1;
}