The Instrument for the Second Messenger: A Runnable Analysis Design for the Diffuse-Neutrino Steepening at 3.02x10^18 eV (PD-892)

The runnable analysis design for sealed prediction PD-892 (a steepening of the diffuse neutrino tail within +-0.1 dex of 3.02e18 eV, step >= 0.5, graded at 2DeltaLL >= 9 on the first >=300-event above-1-EeV data set). Full spec: 0.25-dex bins over 10^17.5-10^19.5 eV, break fixed at the frame's address before unblinding, Cash likelihood ratio with profiled normalization, address-blind blinding protocol with staged unblinding, an 11-step run-book, and decision rules D1-D5. The design's evaluating work (SIMULATED, NOT MEASURED): forward-modelled energy-resolution smearing costs 30-43% of the statistic from sigma = 0 to 0.15 dex; the large step grades at N = 300 at every resolution, but the sealed minimum step (Delta gamma = 0.5) has no headroom - median 9.19 at sigma = 0, below the line already at sigma = 0.05 - so sigma <= 0.05 dex is a hard design requirement, printed with the disclosure that a minimum-step HIT is a favourable-fluctuation outcome. Exposure evaluated in flux-model space: 35-539 km2 sr yr of effective exposure yields 300 events above 1 EeV across the declared cosmogenic exhibit band.