Continuous water-quality records and derived diel-phase metrics for US river stations: July 2026 week and September 2025 - September 2026 replication layer

Derived station-day metrics and analysis code for a study of the diel phase relationship between the un-ionized ammonia fraction and dissolved oxygen in US rivers, and its consequences for fixed-hour compliance sampling. Version 1.4 adds the year-round replication evidence layer: a replication harvest of the same network under the identical primary mask (phase_harmonic_yearly.csv, layers_summary.json) and a sensitivity envelope for the constant-TAN assumption (tan_envelope.json), plus the resubmission figure code. No 1.3 statistic was recomputed differently; all 1.3 values are unchanged. This version is temporarily restricted while the associated manuscript is under review: editors and reviewers reach the files through the access link sent with the submission, and the record will be made open on acceptance.