First test surface for the Electron + Vue 3 app — apps/machine has had
no tests until now (workspace packages cover state-machine, nostr-client,
clink, lnbits). Cassette config #56 shipped untested under the same
posture; #57 (operator fee config consumer) introduces enough load-
bearing parser + state-store logic to want unit coverage, so growing
the test substrate now.
Adds `test` / `test:watch` scripts + vitest devDep + minimal config
that picks up `src/**/*.test.ts` and `electron/**/*.test.ts`. No tests
land here — that comes with the feature commit.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
