fix(render): scroll code block as a whole in preview

src/assets/markdown-override.css

@@ -59,27 +59,28 @@
   padding: 16px;
   margin: 16px 0;
   overflow-x: auto;
+  max-width: 100%;
   font-family: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
   font-size: 85%;
   line-height: 1.6;
   border: 1px solid #d0d7de;
 }
 
+/* Quill 代码块：整块一起横向滚动，不换行 */
 .markdown-body .ql-code-block {
   white-space: pre;
   word-break: normal;
-  overflow-x: auto;
 }
 
-/* Markdown code blocks: horizontal scroll, no wrapping */
+/* Markdown 代码块：整块一起横向滚动，不换行 */
 .markdown-body pre {
   overflow-x: auto;
+  max-width: 100%;
 }
 
 .markdown-body pre code {
   white-space: pre;
   word-break: normal;
-  overflow-x: auto;
 }
 
 .markdown-body.markdown-body-dark .ql-code-block-container {