ci: add cancel-in-progress concurrency to PR helper workflows (#40725)

Co-authored-by: Claude Code <noreply@anthropic.com>

.github/workflows/github-action-validator.yml

@@ -12,6 +12,11 @@ on:
 permissions:
   contents: read
 
+# cancel previous workflow jobs for PRs
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
 
   validate-all-ghas: