/* --- 左侧边栏 --- */
        .sidebar {
            width: 260px;
            border-right: 1px solid var(--border-light);
            display: flex;
            flex-direction: column;
            padding: 24px 16px;
            transition: width 0.3s ease, padding 0.3s ease, opacity 0.2s ease;
            overflow: visible;
            flex-shrink: 0;
            background-color: var(--bg-sidebar);
            position: relative;
        }
        .sidebar.hidden {
            width: 56px;
            padding: 14px 8px;
            opacity: 1;
            border-right: 1px solid var(--border-light);
        }

        .sidebar-brand { display: flex; align-items: center; gap: 8px; font-size: 14px; margin-bottom: 18px; padding: 0 4px; white-space: nowrap; cursor: default; min-height: 32px; }
        .sidebar-brand strong { font-weight: 700; }
        .sidebar-brand span { color: var(--text-muted); }
        .brand-icon-wrap {
            width: 30px;
            height: 30px;
            border-radius: 10px;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            flex-shrink: 0;
            color: var(--text-main);
            transition: background 0.2s;
        }
        .brand-logo { width: 22px; height: 22px; display: block; }
        .brand-open-icon { display: none; }
        .sidebar-collapse-btn,
        .sidebar-more-btn,
        .chat-item-menu-btn {
            border: none;
            background: transparent;
            color: var(--text-muted);
            cursor: pointer;
            border-radius: 9px;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            transition: background 0.15s, color 0.15s;
        }
        .sidebar-collapse-btn {
            width: 30px;
            height: 30px;
            margin-left: auto;
        }
        .sidebar-collapse-btn:hover,
        .sidebar-more-btn:hover,
        .chat-item-menu-btn:hover {
            background: var(--bg-hover);
            color: var(--text-main);
        }
        .sidebar.hidden .sidebar-brand { justify-content: center; padding: 0; cursor: pointer; }
        .sidebar.hidden .sidebar-brand strong,
        .sidebar.hidden .sidebar-collapse-btn { display: none; }
        .sidebar.hidden .sidebar-brand:hover .brand-icon-wrap { background: var(--bg-hover); }
        .sidebar.hidden .sidebar-brand:hover .brand-logo { display: none; }
        .sidebar.hidden .sidebar-brand:hover .brand-open-icon { display: block; }

        .sidebar-mode-nav {
            display: flex;
            flex-direction: column;
            gap: 4px;
            margin-bottom: 18px;
        }
        .sidebar-mode-item {
            width: 100%;
            border: none;
            background: transparent;
            color: var(--text-main);
            cursor: pointer;
            border-radius: 10px;
            padding: 9px 10px;
            display: flex;
            align-items: center;
            gap: 10px;
            font-size: 14px;
            text-align: left;
            transition: background 0.15s, color 0.15s;
        }
        .sidebar-mode-item:hover,
        .sidebar-mode-item.active {
            background: var(--bg-active-chat);
            color: var(--text-main);
        }
        .sidebar-mode-item svg {
            flex-shrink: 0;
        }
        .sidebar.hidden .sidebar-mode-nav {
            align-items: center;
            margin-bottom: 16px;
        }
        .sidebar.hidden .sidebar-mode-item {
            width: 36px;
            height: 36px;
            padding: 0;
            justify-content: center;
        }
        .sidebar.hidden .sidebar-mode-item span {
            display: none;
        }

        .sidebar-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 10px; padding: 0 4px; white-space: nowrap; }
        .sidebar-header h2 { font-size: 12px; font-weight: 600; color: var(--text-muted); margin: 0; }
        .sidebar-actions { position: relative; display: flex; align-items: center; gap: 6px; color: var(--text-muted); }
        .sidebar-more-btn,
        .chat-item-menu-btn { width: 28px; height: 28px; }
        .sidebar-utility-menu,
        .chat-item-menu {
            position: absolute;
            display: none;
            min-width: 150px;
            padding: 8px;
            border: 1px solid var(--border-color);
            border-radius: 12px;
            background: var(--bg-surface);
            box-shadow: 0 14px 36px rgba(0,0,0,0.14);
            z-index: 40;
        }
        .sidebar-utility-menu {
            top: calc(100% + 6px);
            right: 0;
        }
        .sidebar-utility-menu.show,
        .chat-item-menu.show {
            display: flex;
            flex-direction: column;
            gap: 4px;
        }
        .sidebar-utility-menu button,
        .chat-item-menu button {
            border: none;
            background: transparent;
            color: var(--text-main);
            cursor: pointer;
            border-radius: 8px;
            padding: 8px;
            display: flex;
            align-items: center;
            gap: 8px;
            text-align: left;
            font-size: 13px;
            white-space: nowrap;
        }
        .sidebar-utility-menu button:hover,
        .chat-item-menu button:hover {
            background: var(--bg-active-chat);
        }
        .chat-item-menu button.danger {
            color: #c84646;
        }
        .chat-item-menu {
            top: 30px;
            right: 0;
        }

        .chat-list { flex: 1; min-height: 0; overflow-y: auto; display: flex; flex-direction: column; gap: 4px; }
        .sidebar.hidden .sidebar-header,
        .sidebar.hidden .multi-select-bar,
        .sidebar.hidden .chat-list {
            display: none;
        }
        .chat-history-item { position: relative; display: flex; align-items: center; gap: 10px; padding: 8px 12px; border-radius: 8px; font-size: 14px; cursor: pointer; color: var(--text-muted); transition: all 0.2s ease; white-space: nowrap; overflow: visible; }
        .chat-history-item:hover { background-color: var(--bg-hover); color: var(--text-main); }
        .chat-history-item.active { background-color: var(--bg-active-chat); color: var(--text-main); }
        .chat-history-item.selected { background-color: var(--bg-active-chat); color: var(--text-main); }
        .chat-title { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; flex: 1; }
        
        /* 多选 checkbox */
        .chat-checkbox { width: 16px; height: 16px; border: 2px solid var(--border-color); border-radius: 4px; flex-shrink: 0; display: none; align-items: center; justify-content: center; transition: all 0.15s; }
        .multi-select-mode .chat-checkbox { display: flex; }
        .multi-select-mode .chat-history-item { padding-left: 12px; }
        .chat-checkbox.checked { background: var(--black-btn); border-color: var(--black-btn); }
        .chat-checkbox.checked::after { content: ''; width: 4px; height: 8px; border: solid var(--text-on-dark); border-width: 0 2px 2px 0; transform: rotate(45deg); margin-bottom: 2px; }
        
        /* 多选操作栏 */
        .multi-select-bar {
            display: none;
            flex-direction: column;
            gap: 6px;
            padding: 8px 10px;
            background: var(--bg-hover);
            border-radius: 8px;
            margin-bottom: 8px;
            border: 1px solid var(--border-light);
        }
        .multi-select-bar.show {
            display: flex;
        }
        .ms-row-top {
            display: flex;
            justify-content: space-between;
            align-items: center;
            width: 100%;
        }
        .ms-row-top .ms-actions-right {
            display: flex;
            gap: 6px;
        }
        .ms-row-bottom {
            display: flex;
            gap: 6px;
            width: 100%;
        }
        .multi-select-bar .ms-count {
            font-size: 11px;
            color: var(--text-muted);
            font-weight: 500;
        }
        .multi-select-bar .ms-btn {
            font-size: 11px;
            padding: 4px 8px;
            border-radius: 6px;
            border: 1px solid var(--border-color);
            background: var(--bg-surface);
            color: var(--text-muted);
            cursor: pointer;
            transition: all 0.15s ease;
            white-space: nowrap;
            display: inline-flex;
            align-items: center;
            justify-content: center;
        }
        .ms-row-bottom .ms-btn {
            flex: 1;
        }
        .multi-select-bar .ms-btn:hover {
            color: var(--text-main);
            border-color: var(--text-main);
            background: var(--bg-hover);
        }
        .multi-select-bar .ms-btn.danger:hover {
            color: #ff4d4f;
            border-color: #ff4d4f;
            background: #fff1f0;
        }
        .dark-mode .multi-select-bar .ms-btn.danger:hover {
            color: #ff7875;
            border-color: #ff7875;
            background: #2a1215;
        }
        
        .chat-history-icons {
            display: flex;
            align-items: center;
            gap: 4px;
            color: var(--text-muted);
            flex-shrink: 0;
            margin-left: 6px;
            position: relative;
        }
        .chat-item-menu-btn {
            opacity: 0;
            pointer-events: none;
        }
        .chat-history-item:hover .chat-item-menu-btn,
        .chat-history-item.active:hover .chat-item-menu-btn,
        .chat-item-menu-btn:focus {
            opacity: 1;
            pointer-events: auto;
        }
        .chat-history-item:hover .chat-history-icons, .chat-history-item.active .chat-history-icons { display: flex; }

        /* --- 右侧主体 --- */
        .main-content {
            flex: 1;
            display: flex;
            flex-direction: column;
            position: relative;
            min-width: 0;
        }

        .top-nav {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 16px 24px;
            min-height: 60px;
            z-index: 10;
        }

        .nav-left-actions { display: flex; align-items: center; color: var(--text-main); cursor: pointer; }
        .sidebar-toggle-btn { display: none; opacity: 0.7; transition: opacity 0.2s; }
        .sidebar-toggle-btn:hover { opacity: 1; }

        .settings-btn {
            background: none;
            border: 1px solid var(--border-color);
            padding: 6px 12px;
            border-radius: 12px;
            cursor: pointer;
            color: var(--text-muted);
            font-size: 13px;
            transition: all 0.2s;
        }
        .settings-btn:hover { color: var(--text-main); border-color: var(--text-muted); }

        .nav-right-actions {
            display: flex;
            align-items: center;
            gap: 8px;
            flex-shrink: 0;
            align-self: center;
            max-width: 100%;
            width: fit-content;
            margin-top: 14px;
            margin-bottom: max(0px, env(safe-area-inset-bottom, 0px));
            padding: 6px;
            border: 1px solid var(--border-color);
            border-radius: 16px;
            background: color-mix(in srgb, var(--bg-surface) 92%, transparent);
            box-shadow: 0 10px 30px rgba(0,0,0,0.08);
            backdrop-filter: blur(10px);
        }

        .dark-mode-btn {
            background: none;
            border: none;
            cursor: pointer;
            color: var(--text-muted);
            padding: 6px;
            display: flex;
            align-items: center;
            justify-content: center;
            border-radius: 8px;
            transition: all 0.2s;
        }
        .dark-mode-btn:hover {
            color: var(--text-main);
            background-color: var(--bg-hover);
        }

        .sidebar-account {
            position: relative;
            margin-top: auto;
            padding-top: 12px;
        }
        .sidebar-account-card {
            width: 100%;
            border: none;
            border-radius: 14px;
            padding: 9px;
            background: var(--bg-active-chat);
            color: var(--text-main);
            cursor: pointer;
            display: flex;
            align-items: center;
            gap: 10px;
            text-align: left;
            transition: background 0.15s;
        }
        .sidebar-account-card:hover {
            background: var(--bg-hover);
        }
        .account-avatar {
            width: 28px;
            height: 28px;
            border-radius: 50%;
            background: #2d2a22;
            color: #f4efe3;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            flex-shrink: 0;
            font-size: 12px;
            font-style: normal;
            font-weight: 700;
        }
        .account-text {
            min-width: 0;
            display: flex;
            flex: 1;
            flex-direction: column;
            gap: 2px;
        }
        .account-text strong {
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
            font-size: 13px;
        }
        .account-text em {
            color: var(--text-muted);
            font-size: 11px;
            font-style: normal;
        }
        .account-arrow {
            color: var(--text-muted);
            transform: rotate(90deg);
            flex-shrink: 0;
        }
        .account-menu {
            position: absolute;
            left: 0;
            right: 0;
            bottom: calc(100% + 8px);
            display: none;
            flex-direction: column;
            gap: 4px;
            padding: 10px;
            border: 1px solid var(--border-color);
            border-radius: 16px;
            background: var(--bg-surface);
            box-shadow: 0 16px 42px rgba(0,0,0,0.14);
            z-index: 30;
        }
        .account-menu.show {
            display: flex;
        }
        .account-menu-profile {
            display: flex;
            align-items: center;
            gap: 10px;
            padding: 6px 6px 10px;
            border-bottom: 1px solid var(--border-color);
            margin-bottom: 4px;
        }
        .account-menu-profile div {
            min-width: 0;
            display: flex;
            flex-direction: column;
            gap: 2px;
        }
        .account-menu-profile strong {
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
            font-size: 13px;
        }
        .account-menu-profile span {
            color: var(--text-muted);
            font-size: 12px;
        }
        .account-menu button {
            border: none;
            background: transparent;
            color: var(--text-main);
            cursor: pointer;
            border-radius: 10px;
            padding: 9px 8px;
            display: flex;
            align-items: center;
            gap: 10px;
            font-size: 13px;
            text-align: left;
        }
        .account-menu button:hover {
            background: var(--bg-active-chat);
        }
        .sidebar.hidden .sidebar-account-card {
            width: 36px;
            height: 36px;
            padding: 0;
            justify-content: center;
        }
        .sidebar.hidden .account-text,
        .sidebar.hidden .account-arrow,
        .sidebar.hidden .account-menu {
            display: none;
        }