CI has failed on every merge to main, but PRs keep merging — main needs a required status check #500

Problem

gh run list -b main shows the last five pushes to main (merges of #454, #456, #453, #467 and #469 on 2026-09-27/28) all ended in failure. main now doesn't type-check, and 17 of 47 Jest suites fail even after patching the three syntax errors. Breakage accumulated because nothing stops a PR merging while the pipeline is red.

Suggested fix

Turn on branch protection for main that requires the CI Pipeline job and requires branches to be up to date before merging. Most of the merge damage here comes from PRs that were green against an older main.

Related: #156