Tests and coverage

Every file exporting code has a spec next to it (format-number.ts → format-number.spec.ts), run by Vitest. The check fails below 100 % coverage of lines, branches, functions and statements.

• Each API page lists the tests of its function, with their result from the last build, and its line coverage.
• The SVG specs render real SVG in Chromium (the browser project of Vitest, through Playwright): run pnpm exec playwright install chromium once; the CI installs it at each run.
• The full coverage report shows every line and branch.
• pnpm test runs the specs, pnpm coverage adds the coverage report.
• pnpm check runs everything before a push: catalog, types, lint, format, unused code, tests with coverage.