Step 27 of v4.3 plan — adds Playwright 1.59.1 + axe-core/playwright 4.10.2
as devDependencies, npm script test:e2e, and playwright.config.mjs with
file:// baseURL pointing at playground/. Chromium browser binary installed
to ~/Library/Caches/ms-playwright/.
Trace: SC2 (WCAG verifikasjon krever browser-driver), research/04
Recommendation security; brief Constraint linje 64 (zero new deps i
playground/) er OK fordi Playwright er devDependency på voyage-plugin-rot,
ikke i playground/.
