4c475f2b0e
Add a webkit project to the Playwright config so the hermetic mock-mode specs run in both Chromium and WebKit, and install both browsers in CI. WebKit's Debian build runs headless without extra host system libraries (verified locally: smoke + zoom pass in webkit); the workflow comment records the one-time host install-deps fallback if a runner ever lacks a library. Desktop WebKit does not reproduce iOS Safari's text auto-inflation, so the app.css text-size-adjust guard stays outside e2e coverage.