The Research Landscape Around the Riemann Hypothesis in Light of the Structural Classification

Companion to 'The Riemann Hypothesis as a Fixed-Point Phenomenon' (doi:10.5281/zenodo.19425929) and 'Below the Threshold' (doi:10.5281/zenodo.19426045). We apply the D1-D4 structural classification and the resolution threshold to the major research programs around the Riemann Hypothesis: zero-density estimation, random matrix theory, sieve methods, the Hilbert-Polya conjecture, and the Langlands program. Each program is located relative to the resolution threshold. Programs producing proved results operate below the threshold; programs that stall engage the structural obstruction. The finite-field case (Weil-Deligne), where the structural type is fully resolved, serves as a controlled comparison. Five testable predictions are stated. No theorems are proved; the contribution is the organizing observation that the classification produces a coherent account of 165 years of results and stalls.