fix: Correctly render multiple think blocks in Markdown (#18310)

Co-authored-by: xzj16125 <xuzijie@noahgroup.com>
Co-authored-by: crazywoola <427733928@qq.com>

web/app/components/base/markdown.tsx

@@ -85,9 +85,11 @@ const preprocessLaTeX = (content: string) => {
 }
 
 const preprocessThinkTag = (content: string) => {
+  const thinkOpenTagRegex = /<think>\n/g
+  const thinkCloseTagRegex = /\n<\/think>/g
   return flow([
-    (str: string) => str.replace('<think>\n', '<details data-think=true>\n'),
-    (str: string) => str.replace('\n</think>', '\n[ENDTHINKFLAG]</details>'),
+    (str: string) => str.replace(thinkOpenTagRegex, '<details data-think=true>\n'),
+    (str: string) => str.replace(thinkCloseTagRegex, '\n[ENDTHINKFLAG]</details>'),
   ])(content)
 }