fix(ci): use is-ci-cli binary so npm test actually runs Jest

[arb]

What and why

Surprising bug: npm test has been silently green-without-tests in CI for some time. Across every matrix cell on master (ae850d0), the test step prints > is-ci 'test:ci' 'test:local' and exits in ~0.1s without ever invoking Jest. No Tests: N passed line, no coverage written.

Root cause

Two installed packages publish a binary called is-ci:

1. The standalone is-ci package, pulled in transitively. Its bin is literally:

   process.exit(require('./') ? 0 : 1)

   It exits 0 in CI, 1 otherwise. Arguments are ignored.

2. Our is-ci-cli devDep, which exposes both is-ci and is-ci-cli binaries pointing at the same cli.js (the one that actually spawns the named npm script).

When both are installed, node_modules/.bin/is-ci wins for whichever package was linked last. In this repo it's the standalone package:

node_modules/.bin/is-ci -> ../is-ci/bin.js

So "test": "is-ci 'test:ci' 'test:local'" invoked the dummy bin and silently succeeded. The is-ci-cli README documents the correct invocation as the unambiguous binary is-ci-cli -- using that name avoids the collision entirely.

The fix

One word in package.json:

-    "test": "is-ci 'test:ci' 'test:local'",
+    "test": "is-ci-cli test:ci test:local",

(Quotes also dropped to match the package's documented usage; no spaces in the script names.)

Local verification

$ rm -rf coverage && CI=true npm test
> is-ci-cli test:ci test:local
> node --experimental-vm-modules node_modules/.bin/jest --ci
...
All files          |     100 |      100 |     100 |     100 |
Test Suites: 2 passed, 2 total
Tests:       62 passed, 62 total
$ ls -la coverage/lcov.info
-rw-r--r-- 1 ... 2259 ... coverage/lcov.info

Related

Unblocks #262 (codecov-action migration) -- once both merge, the new coverage job will actually have an lcov.info file to upload.