use sparse checkout in PR title workflow for improved performance

Author: allnes

.github/workflows/check-pr-title.yml

@@ -17,10 +17,14 @@ jobs:
       github.event.action != 'edited' ||
       contains(toJson(github.event.changes), 'title')
     steps:
-      - name: Check out base branch (for script)
+      - name: Checkout repository (sparse, PR head)
         uses: actions/checkout@v5
         with:
-          ref: ${{ github.event.pull_request.base.ref }}
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 1
+          sparse-checkout: |
+            scripts
+          sparse-checkout-cone: true
       - name: Run PR title check
         run: |
           python3 scripts/check_pr_title.py "${{ github.event.pull_request.title }}"