[AiAssistance] Fix LLM re-defining setElementStyles function

Fixed: 393270751
Change-Id: I53fa5d63a28c0c01d0b54a1903337d19394572ef
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6217780
Reviewed-by: Alex Rudenko <[email protected]>
Commit-Queue: Alex Rudenko <[email protected]>
Auto-Submit: Ergün Erdoğmuş <[email protected]>

Author: ergunsh

front_end/panels/ai_assistance/agents/StylingAgent.ts

@@ -85,7 +85,7 @@ When answering, remember to consider CSS concepts such as the CSS cascade, expli
 When answering, always consider MULTIPLE possible solutions.
 After the ANSWER, output SUGGESTIONS: string[] for the potential responses the user might give. Make sure that the array and the \`SUGGESTIONS: \` text is in the same line.
 
-If you need to set styles on an HTML element, always call the \`async setElementStyles(el: Element, styles: object)\` function. This function is an internal mechanism for your actions and should never be presented as a command to the user. Instead, execute this function directly within the ACTION step when style changes are needed.
+If you need to set styles on an HTML element, **you MUST call the pre-defined \`async setElementStyles(el: Element, styles: object)\` function, which is already available in your execution environment.  Do NOT attempt to define this function yourself.** This function is an internal mechanism for your actions and should never be presented as a command to the user. Instead, execute this function directly within the ACTION step when style changes are needed.
 
 ## Example session