GitLab

Wires up vitest + @vue/test-utils + jsdom so the spec 0004 tests can run.

- package.json: 3 npm scripts (test, test:run, test:ui) + vitest /
  @vue/test-utils / jsdom devDeps.
- vitest.config.js: jsdom env, @ alias pointing at src/, setup file.
- src/test-setup.js: shared jest-dom-style matchers.
- src/__tests__/smoke.test.js: sanity check the harness resolves the @
  alias and that taskService imports cleanly.
Co-Authored-By: Claude <noreply@anthropic.com>