ci: scope PR merge guidance concurrency per PR (#2041)

Author: Pouyanpi

.github/workflows/pr-merge-guidance.yml

@@ -25,7 +25,7 @@ permissions:
   pull-requests: write
 
 concurrency:
-  group: pr-merge-guidance-${{ github.repository }}
+  group: pr-merge-guidance-${{ github.event.pull_request.number || github.event.inputs.pr_number || github.ref_name }}
   cancel-in-progress: false
 
 jobs: