[test]: Add Automated Test Setup (Jest or Vitest)

### Problem
No automated tests currently exist (`npm test` always exits with an error).

### Proposed Work
- Add a test framework and base configuration.
- Add unit tests for at least one command and one database helper.
- Update `package.json` `test` script to run real tests.

### Acceptance Criteria
- `npm test` executes and returns pass/fail based on tests.
- At least 3 meaningful tests are included.

Start with package.json and run npm test to confirm the current failure. Inspect the existing command entry points and database helper to choose one of each for coverage, then add the test framework configuration and at least three meaningful tests. Done means npm test returns pass/fail from the new tests.

Written by the indexing model from the issue text.