Add checkout step

Author: jgchn

.github/workflows/run-examples-prep.yml

@@ -14,6 +14,10 @@ jobs:
     #     python-version: ['3.11', '3.12', '3.13']
 
     steps:
+    - uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+        ref: ${{ github.event.pull_request.head.ref }}
 
     - name: Push the new run-examples yaml config 
       shell: bash