* test(web): standardize frontend tests on Vitest
- configure Vitest, jsdom, and React Testing Library with shared test scripts.
- migrate existing node:test suites to the Vitest runner.
- rewrite JsonCodeEditor component tests with RTL and remove the direct happy-dom dependency.
* fix(ci): run frontend tests with Vitest
- invoke the configured Vitest script so browser test setup loads in CI.
- migrate remaining node:test suites to Vitest lifecycle APIs.
* test(web): use shared jsdom environment for component tests
- migrate usage cost and tool price tests to React Testing Library.
- remove duplicate happy-dom globals and rely on the configured Vitest setup.
* test(web): verify behavior with shared vitest setup
- replace Node test assertions with Vitest expect across frontend suites.
- migrate Keys component tests to React Testing Library interactions.
- centralize jsdom browser mocks for consistent component execution.
* fix(web): unblock frozen installs and Vitest CI
- sync dompurify 3.4.13 metadata into the Bun lockfile.
- replace the bun:test and happy-dom redemption harness with Vitest and RTL.
- preserve quota conversion, error feedback, and stale-response coverage in jsdom.
