G17 -- A rewritten history is not private until the host has purged the objects

The host's own metadata (an activity view, event feeds, pull-request refs) publishes every pre-force-push tip, and each still serves the old tree. A visibility flip is gated on a probe of the old object ids — or on recreating the repository — never on a clean working tree. provenance: BFM R82; 157 activity rows still serving the executable after the force-push