nx_msg_sync_gate.nx

nx_msg_sync_gate.nx -- REFEREE for C2 (nx_msg_sync, contract msy_devsync). END-TO-END: builds a server room and device replicas in /tmp/msgate (nothing production is touched), forks BOTH promoted elfs -- nx_chat_store to author fixtures and READ BACK, nx_msg_sync as the subject -- and proves the pre-declared done-rule: "the same history converges on a second device; a partition-printed reconcile measures zero divergence." THE ANTI-VACUITY DESIGN: convergence is NEVER taken from the syncer's own receipt. T3/T5 compare nx_chat_store fetch output on the server root vs the device root BYTE FOR BYTE -- the consumer is the referee, so a syncer that lied about pulling would fail the tooth it cannot see. NEGATIVE CONTROLS: split-brain divergence refuses (seq named, nothing written) · device-ahead refuses · absent source never conjures · verify itself goes RED on the diverged replica. Fixture rooms are epoch-suffixed; every verb is its own fork, so persistence across process death is structural. license_tier: ORIGINAL expect_exit: 0