Jest force-stopped worker processes that could not exit within 500 ms on
a starved CPU, failing runs where every test passed. The test scripts now
pass --runInBand. script/lib/jest.js fails the run at once when jest
warns that it did not exit one second after the run, instead of
hanging. The Dockerfile test stage drops its 90-second timeout.
tests/jestRunner.test.js runs the runner on a fixture that leaves an
interval running and expects exit status 1.
Model: opus-5-5
