Terminal Altitude Architecture and Post-Selection Artifacts in Adjacent Zeta-Zero Spacing

We re-examine extreme adjacent-spacing tail packets among Riemann zeta zeros in the terminal LMFDB band using a seam-stitched board of \terminalrows{} rows spanning approximately \(\terminalmin\) to \(\terminalmax\). Earlier exploratory projections suggested two positive structures: a narrow first-logarithmic-harmonic \(h_1\) corridor and a discrete row-sector structure centered on modulus \(1009\). Subsequent search-adjusted validation audits show that neither interpretation survives as an explanatory mechanism. The circular resultant \(R\) is reproduced or exceeded by packet-count-matched search-adjusted synthetic and permutation controls; the apparent \(h_1\)-specific Arc80 corridor is absorbed by rank-altitude and altitude-matched controls; and the \(M=1009\) sector signal fails a dense \(M=800,\ldots,1200\) search-adjusted permutation null.

The surviving empirical object is a robust and predictive terminal altitude architecture in extreme adjacent-spacing tail activity. A primary reconstructed packet population contains \(\primarypackets\) high-tail packets under the fitted-ratio metric. Its yield rate is strongly non-uniform after normalization by board-row density, with a stable high-yield ridge near \(T\approx \primarypeak\), broad cold bands in the mid-terminal range, and multi-component descriptive altitude structure. Cross-threshold validation shows that hot altitude bands learned from looser packet thresholds predict held-out stricter packets with enrichment ratios from approximately \(1.69\) to \(1.98\) and permutation probabilities near \(10^{-3}\). The architecture is tail-general rather than compression-only: hot bands trained on one fitted-ratio tail also enrich the opposite tail, although the two tails have shifted altitude distributions. Altitude-only and hot-band surrogate packet sets reproduce the previously observed \(h_1\) Arc80 corridor, showing that \(h_1\) is a descriptive projection of altitude localization rather than a coordinate-specific phase resonance.

A short forward extrapolation beyond the current endpoint forecasts cold continuation immediately after \(T\approx30.610043\mathrm{B}\), with the first primary forecast bin at approximately \(0.40\times\) the observed global packet-yield rate and no forecast hot bins through \(T\approx\forecastend\). This extrapolation is not used as evidence in the present paper; it is recorded only as a falsifiable target for future zero-table extensions. The resulting claim is finite-horizon and deliberately narrower than the original preprints: the terminal band contains a cross-validated altitude architecture of extreme tail activity, while the earlier \(h_1\) and modulus-\(1009\) structures are examples of visually compelling post-selection artifacts in high-dimensional exploratory analysis of zeta-zero spacings.