FF150+Fission auto-loads about:newtab (TopSitesFeed) ~100ms-1s after a tab's
first navigation — a cross-process BC swap that replaces the page. The wrapper
always disables this (prefs.py); the raw-Playwright drive gate did not, so any
action that adds latency (e.g. the human-cursor motion path) let the page vanish
mid-sequence and surfaced as a phantom "waiting for locator" timeout — an
environment artifact, not a binary defect. The gate now launches with the same
newtab-suppression prefs every real run uses.
Add republish.yml: re-gate + publish an existing build run's artifacts without
rebuilding, for when all builds succeeded but a gate/test bug blocked publish.
