ai: Remove comment code in CSS.

* Sometimes showed on chatbot in reasoning mode.

src/ui/reasoning.py

@@ -69,7 +69,7 @@ def styles(reasoning: str, content: str, expanded: bool = False) -> str:
     line-height: 1.7;            /* Increased line height for easy text flow */
     letter-spacing: 0.02em;      /* Slight letter spacing to enhance legibility */
   ">
-    {reasoning}                 <!-- Reasoning -->
+    {reasoning}
   </div>
 </details>
 """