Update ci.yml: Handle both PRs and commits to main

.github/workflows/ci.yml

@@ -49,4 +49,8 @@ jobs:
     - name: Push changes
       if: success()
       run: |
-        git push origin HEAD:${{ github.event.pull_request.head.ref }}
+        if [ "${{ github.event_name }}" = "pull_request" ]; then
+          git push origin HEAD:${{ github.event.pull_request.head.ref }};
+        else
+          git push origin HEAD:main;
+        fi