chore(aida): align PR body template with gdc-aida

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
JIRA: DX-340
risk: low

Author: jaceksan

.aida/templates/pr-body.md

@@ -1,11 +1,8 @@
-# PR template generated by AIDA onboarding.
-# Detected ticket prefix usage in history (DX-123 pattern).
-
 ## Summary
-- {summary}
+{summary}
 
 ## Test plan
-- {test_plan}
+{test_plan}
 
 {co_authored_by}
 {ticket}