- attach the asserted context to every same-origin request inside the
three fetch entries, so no call site classifies itself
- discard a response whose echoed context contradicts the adopted one;
serve one that carries no echo, which is what keeps the public poll
and every actor surface working
- adopt from /api/auth/me and the switch response, and from nothing else
- send the epoch on every switch and retry once after reconciling
- hold and reconcile on the 409 instead of leaving the record