Merge pull request #4473 from Shopify/andychhuon/deploy-changesets-push-guard-2026-04

ci: gate Deploy changesets job to push events only (2026-04)

Author: andy-chhuon

.github/workflows/deploy.yml

@@ -56,6 +56,7 @@ jobs:
 
   changesets:
     name: Deploy
+    if: ${{ github.event_name == 'push' }}
     runs-on: ubuntu-latest
     permissions:
       contents: read