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.
System libs are now provisioned once on the runner host (install-deps); the job
downloads the browser into the runner cache and runs the smoke strictly (no
--with-deps, no sudo, no continue-on-error; timeouts kept as a hang guard).
The Gitea runner is an act host executor without apt privileges, so
'playwright install --with-deps chromium' (apt-get) hung ~51m then failed. Drop
--with-deps, bound the browser-install + e2e steps with timeouts and mark them
continue-on-error so a runner lacking GUI libs can't block the gate. The strict
gate stays check/unit/build/size; the e2e smoke remains a hard local pre-push check.