Freeze licensed chest X-ray sources and patient-disjoint splits

Freeze licensed chest X-ray sources and patient-disjoint splits

Record the license terms for each chest X-ray source, define the pneumonia label, and split the data so that no patient appears twice and one hospital is held out entirely. Log every excluded study with a reason. Deliverable: A split manifest with patient, study, and hospital counts, a license record, and a statement that the split alone yields no accuracy result.