Add tab reordering, sidebar resize and collapse, and outline panel

- Drag tabs to reorder; context menu to close, close others, close right
- Resizable sidebar width (synced setting), collapsible with Mod+\
- Outline panel (Mod+Shift+O): right column on desktop, overlay on mobile
- Mobile: title opens quick switcher, swipe left closes the drawer,
  44px touch targets

web/src/app/app.css

@@ -106,12 +106,26 @@ button {
 /* ---- 布局 ---- */
 .rm-shell { display: flex; height: 100%; }
 .rm-sidebar {
+  position: relative;
   width: var(--rm-sidebar-width);
   flex: none;
   background: var(--rm-sidebar-bg);
   border-right: 1px solid var(--rm-divider);
 }
 .rm-main { flex: 1; min-width: 0; display: flex; flex-direction: column; }
+.rm-sidebar-resize { position: absolute; top: 0; right: -3px; bottom: 0; width: 6px; cursor: col-resize; z-index: 5; touch-action: none; }
+.rm-sidebar-resize:hover,
+.rm-sidebar-resize:active { background: var(--rm-accent); opacity: 0.4; }
+.sidebar-collapsed .rm-sidebar { display: none; }
+
+/* ---- 大纲 ---- */
+.rm-outline-backdrop { display: contents; }
+.rm-outline { flex: none; width: 240px; display: flex; flex-direction: column; border-left: 1px solid var(--rm-divider); background: var(--rm-sidebar-bg); }
+.rm-outline-head { display: flex; align-items: center; justify-content: space-between; padding: 10px 8px 6px 16px; font-size: 13px; font-weight: 600; color: var(--rm-text-muted); }
+.rm-outline-list { flex: 1; overflow-y: auto; list-style: none; margin: 0; padding: 0 6px 12px; }
+.rm-outline-list li { padding-top: 5px; padding-bottom: 5px; padding-right: 8px; border-radius: 6px; font-size: 13px; line-height: 1.4; cursor: pointer; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+.rm-outline-list li:hover { background: var(--rm-hover); }
+.rm-outline-list li.on { color: var(--rm-accent-strong); background: var(--rm-active); }
 .rm-backdrop,
 .rm-mobile-bar { display: none; }
 
@@ -284,7 +298,15 @@ button {
   scrollbar-width: none;
   flex: none;
 }
-.rm-tabs:empty { display: none; }
+.rm-tabs.empty { display: none; }
+.rm-tabs-side,
+.rm-tabs-outline { flex: none; align-self: center; margin-bottom: 4px; }
+.rm-tabs-outline { margin-left: auto; position: sticky; right: 0; background: var(--rm-bg); }
+.rm-tabs-outline.on { color: var(--rm-accent-strong); }
+.rm-tab.dragging { opacity: 0.5; }
+.rm-tab.drop-before { box-shadow: inset 2px 0 0 var(--rm-accent); }
+.rm-tab.drop-after { box-shadow: inset -2px 0 0 var(--rm-accent); }
+.rm-tab-menu { position: fixed; z-index: 20; min-width: 160px; }
 .rm-tab {
   display: flex;
   align-items: center;
@@ -479,13 +501,20 @@ button {
     border-bottom: 1px solid var(--rm-divider);
     flex: none;
   }
-  .rm-mobile-bar .rm-icon-btn { width: 40px; height: 40px; }
-  .rm-mobile-title { flex: 1; font-weight: 600; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+  .rm-mobile-bar .rm-icon-btn { width: 44px; height: 44px; }
+  .rm-mobile-title { flex: 1; min-width: 0; height: 40px; padding: 0 4px; border: 0; background: none; color: var(--rm-text); font: inherit; font-weight: 600; text-align: left; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+  .sidebar-collapsed .rm-sidebar { display: block; }
+  .rm-sidebar-resize { display: none; }
+  /* 大纲在手机上为从右侧滑入的浮层 */
+  .rm-outline-backdrop { display: block; position: fixed; inset: 0; z-index: 41; background: rgba(0, 0, 0, 0.3); }
+  .rm-outline { position: absolute; top: 0; right: 0; bottom: 0; width: min(80vw, 300px); padding-top: env(safe-area-inset-top); box-shadow: var(--rm-shadow); }
+  .rm-outline-list li { padding-top: 12px; padding-bottom: 12px; font-size: 15px; }
   .rm-save-state { width: 8px; height: 8px; margin-right: 8px; border-radius: 50%; background: transparent; }
   .rm-save-state.on { background: var(--rm-accent); }
-  .rm-tree-row { height: 40px; font-size: 15px; }
-  .rm-tree-more { opacity: 1; width: 36px; height: 36px; }
-  .rm-sidebar-head .rm-icon-btn { width: 40px; height: 40px; }
+  /* 触控热区不小于 44px */
+  .rm-tree-row { height: 44px; font-size: 15px; }
+  .rm-tree-more { opacity: 1; width: 44px; height: 44px; }
+  .rm-sidebar-head .rm-icon-btn { width: 44px; height: 44px; }
   /* 小于 16px 时 iOS Safari 聚焦输入框会自动放大页面 */
   .rm-search-input { height: 40px; font-size: 16px; }
   .rm-auth-card input,