test.yml: npm test masks pi-extension failures when root tests fail

In `.github/workflows/test.yml` line 34: The `npm test` script chains two test suites: ```json "test": "node --test tests/*.test.js && npm test --prefix pi-extension" ``` With `&&`, if root tests fail, pi-extension tests are **never run** — failures are silently masked. Fix: split into two separate workflow steps so both always execute regardless of the other's result.