ui: run local browser tests in installed Chrome with its sandbox on (#31596)
Playwright's bundled Chromium lags behind Chrome security releases
(1.56.1 ships 141, and even 1.64.1 ships 156.0.8078.4, before the
156.0.8078.73 fixes), and Playwright launches it with --no-sandbox by
default. Outside CI, use the installed, auto-updated Chrome with the
sandbox enabled. CI keeps the bundled Chromium, so the self-hosted
runner's preinstalled 1.56.1 browsers still work.
Assisted-by: Claude (Opus 5.5 Medium)