- Add vitest as dev dep (pnpm add -D vitest), create vitest.config.ts
with globals:true and setupFiles
- Migrate digest-template, normalize-relay-url, reschedule-on-frequency-change,
and event-arrival-race from raw JS + hand-rolled asserts to vitest
describe/it/expect, as .test.ts (port all assertions without weakening)
- Create test/setup.ts with env vars needed by env.ts/mailer.ts
- DELETE test/web-ui.test.js: dead test for removed web UI (PR #1)
- package.json: add test:unit script (vitest run), keep test = bash E2E
- script/checks: add pnpm test:unit after build
- README: document pnpm test:unit / pnpm test
