.github/workflows/preview.yml: Ensure preview is recreated on PR merges
When a PR is merged, we want the preview to be automatically updated.
GitLab Maintenance scheduled for Thursday, 18th December 2025, from 7:00 AM to 10:00 AM BST. GitLab will be in read-only mode and experience short periods of complete downtime (up to 20 minutes) during this window.
When a PR is merged, we want the preview to be automatically updated.