gh pr merge --auto fires on MERGEABLE even while checks are UNSTABLE — you can merge a PR with failing tests

Using gh pr merge <n> --auto --merge to "merge when green". The PR merged immediately even though its CI was still UNSTABLE (Unit Tests / Typecheck pending), and a unit-test failure that was running at the time landed on the default branch — turning it red. You expected --auto to wait for all checks to pass.