test: make test fails when jest force-stops a worker (closes #711)

When a test leaves a timer running, jest force-stops the worker that ran
the test, prints a warning, and the run still passes. Jest has no option
that fails the run instead. Both test scripts in package.json now run
jest through script/lib/jest.js. Jest runs inside that file's process,
so its terminal output stays the same. The file exits 1 when jest
printed that warning.

Model: opus-5-5

package.json

@@ -6,8 +6,8 @@
     "license": "GPL-3.0",
     "private": true,
     "scripts": {
-        "test": "jest --maxWorkers=3",
-        "test:verbose": "jest --maxWorkers=3 --verbose",
+        "test": "node script/lib/jest.js --maxWorkers=3",
+        "test:verbose": "node script/lib/jest.js --maxWorkers=3 --verbose",
         "build": "node build.js",
         "lint": "eslint . && prettier --check .",
         "fmt": "prettier --write .",