iOS Shared-Tab-Group join — zero-gesture trigger

This page performs a script-initiated top-level navigation to the Chrome Shared-Tab-Group share URL with no user interaction. On iOS Chrome (with the SharedTabGroupsIOS field trial active and a signed-in consumer account), the DataSharingTabHelper gesture gate at ShouldHandleShareURLNavigation() is a no-op, so the browser will dismiss any open modal and present the ShareKit "Join shared tab group" sheet without any tap.

Navigating in 1s with NO user gesture…