PR merged before follow-up commits were pushed: rebase leftovers onto master as a new PR

Situation: user merged a GitHub PR while more local commits on the same branch were unpushed. The remote branch got deleted after the merge, and master contained the PR only up to the old head.

Fix: git fetch, then git checkout -b new-branch && git rebase --onto origin/master <merged-head-sha>. This replays only the unmerged commits. Push and open a follow-up PR.

Check the old branch is fully contained before deleting it with git cherry -v new-branch old-branch; no + lines means every patch is present. A plain git diff old new can show a non-empty diff just from unrelated commits that landed on master, so it is not a safe test.

Symptom the user noticed: the deployed site lacked features (static PNG charts instead of interactive Chart.js) because those commits never reached master.