fix: 知识点公式解析 bug 跟踪。

app/Services/KatexRenderer.php

@@ -185,6 +185,10 @@ class KatexRenderer
                 $decoded = html_entity_decode($tex, ENT_QUOTES, 'UTF-8');
             }
 
+            // 清理公式内部的换行与 <br>，避免 \frac{M}\n{N} 破坏解析
+            $tex = preg_replace('/<br\\s*\\/?>/i', '', $tex);
+            $tex = preg_replace('/\\r\\n|\\r|\\n/', '', $tex);
+
             return $this->fixCasesLineBreaks($tex);
         };