Replication and protocol record for "Clearance rather than ceiling: when does urban morphology constrain drone delivery? A cross-city three-dimensional accessibility study"

Protocol record, analysis code, derived result tables, figures and manuscript sources for a cross-city three-dimensional accessibility study of low-altitude drone delivery across 20 Chinese cities, with New York City as an external stress test. Includes the frozen definition registry, the pre-registration amendment, the frozen prediction models and blind holdout predictions, a claim-to-data-to-code crosswalk, an environment lock file, and SHA-256 manifests. Third-party input datasets (building footprints and heights, terrain, points of interest) are cited in the manuscript and are not redistributed.