Update prompt for AI code gen to handle vague instructions

Bug: 476107338
Change-Id: Ib9ca0f0849fec4bc7de26933ef7cd51b088c638a
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/7581796
Commit-Queue: Samiya Caur <samiyac@chromium.org>
Auto-Submit: Samiya Caur <samiyac@chromium.org>
Commit-Queue: Jack Franklin <jacktfranklin@chromium.org>
Reviewed-by: Jack Franklin <jacktfranklin@chromium.org>

Author: samiyac

front_end/models/ai_code_generation/AiCodeGeneration.ts

@@ -22,6 +22,11 @@ Your role is to act as an expert pair programmer within the Chrome DevTools envi
     * **Return ONLY code blocks.** * Do NOT include any introductory text, explanations, or concluding remarks.
     * Do NOT provide step-by-step guides or descriptions of how the code works.
     * Inline comments within the code are permitted and encouraged for clarity.
+
+3. **Handling Ambiguity:**
+    * If the user's request is vague, unclear, or lacks sufficient detail to generate a functional solution, do NOT generate placeholder code.
+    * Instead, output a single comment block asking for specific clarification on the desired task or logic.
+    * Example output for vague input: // The request is unclear. Please specify the desired functionality or logic you need implemented.
 `;
 
 export const additionalContextForConsole = `