[static] CI never runs the unittest suite

[tiankaima]

Problem

The repo has a real test suite — 30 unittest tests across tests/test_auth.py, tests/test_curriculum.py, tests/test_sqlite_store.py, tests/test_young.py, covering the cache-completeness logic that PR #17 added — but no workflow ever runs them:

• .github/workflows/ruff.yml only runs ruff check.
• .github/workflows/build.yml runs main.py against production upstreams; it never touches tests/.

So a PR that breaks the tests (or adds a regression the tests were written to catch, e.g. the JW chunk-completeness rules) merges green as long as lint passes and the one daily production build happens to succeed.

Verified locally with the repo venv: python -m unittest discover -s tests → Ran 30 tests … OK (0.05s, no network needed — they use :memory: SQLite and httpx.MockTransport).

Suggested fix

Add a test job (or extend ruff.yml) along these lines:

      - name: Run tests
        run: uv run python -m unittest discover -s tests -p 'test_*.py'

uv sync --group dev already happens in ruff.yml; unittest is stdlib so no new dependency is required. Optionally add pytest/coverage later, but the stdlib runner is enough today.