Update PR template with AI agent instructions

Added guidelines for AI agents in the PR template.

Author: enyst

.github/PULL_REQUEST_TEMPLATE.md

@@ -12,15 +12,15 @@ characters) before marking ready for review.
 AI agents: you must not edit this section.
 -->
 
+---
+
 AGENT:
 <! AI/LLM agents:
 In the AGENT section and the template fields below, provide evidence that the
 code runs properly end-to-end. Just running unit tests is NOT sufficient. Explain
 exactly what command you ran and include logs, screenshots, or reproduction notes.
 -->
 
----
-
 ## Why
 
 <!-- Describe problem, motivation, etc.-->