opt: 8项优化——搜索高亮精度/滚动同步/行号同步/本地图片/拖拽提示/MRU标签/侧边栏调宽/toast组件

renderer/style.css

@@ -750,6 +750,7 @@ html, body {
   flex-shrink: 0;
   overflow: hidden;
   user-select: none;
+  position: relative;
 }
 
 #sidebar.collapsed {
@@ -1064,3 +1065,46 @@ html, body {
 .welcome-content {
   animation: fadeIn 0.3s ease;
 }
+
+/* ===== Toast Notification ===== */
+#toast-notification {
+  position: fixed;
+  bottom: 40px;
+  left: 50%;
+  transform: translateX(-50%) translateY(20px);
+  background: var(--text);
+  color: var(--bg);
+  padding: 8px 20px;
+  border-radius: 6px;
+  font-size: 13px;
+  font-family: var(--font-ui);
+  box-shadow: var(--shadow-lg);
+  opacity: 0;
+  pointer-events: none;
+  transition: opacity 0.3s ease, transform 0.3s ease;
+  z-index: 9999;
+  max-width: 480px;
+  text-align: center;
+}
+
+#toast-notification.show {
+  opacity: 1;
+  transform: translateX(-50%) translateY(0);
+  pointer-events: auto;
+}
+
+/* ===== Sidebar Resize Handle ===== */
+.sidebar-resize-handle {
+  position: absolute;
+  top: 0;
+  right: -2px;
+  width: 4px;
+  height: 100%;
+  cursor: col-resize;
+  z-index: 5;
+}
+
+.sidebar-resize-handle:hover,
+.sidebar-resize-handle:active {
+  background: var(--primary);
+}