The originating relay (where the caller is) never set peer_relay_fp
because the call was created locally. When the callee's answer
arrived via federation, the cross-relay dispatcher handled it but
didn't mark the call as cross-relay. This meant the caller's
MediaPathReport was delivered via local hub.send_to() to a peer
fingerprint that isn't connected locally — silently dropped.
Fix: in the cross-relay answer dispatcher, call
reg.set_peer_relay_fp(call_id, Some(origin_relay_fp)) so the
originating relay knows to forward MediaPathReport via federation.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>