Data model update - add the `*_source_text` fields - approved

[lindaxiang]

• All “*_source_text” fields are optional and intended to preserve verbatim input from the source records
• Preserve "source_text" for auditing and future model training of AI-assisted ontology mapping

Field Name	Description
disease_source_text	Free-text disease description as originally recorded in the source system, prior to ontology mapping.
drug_source_text	Free-text drug name or description as recorded in the source, prior to normalization or ontology mapping.
procedure_source_text	Free-text description of the procedure as entered in the source data, before mapping to standardized terms.
procedure_body_site_source_text	Free-text description of the anatomical site for a procedure, as originally captured in the source.
radiation_modality_source_text	Free-text description of the radiation modality as provided in the source record, before mapping to controlled terms.
anatomical_site_irradiated_source_text	Free-text description of the anatomical site irradiated, as originally recorded in the source.
phenotype_source_text	Free-text description of a phenotype or clinical feature, prior to ontology mapping.
comorbidity_source_text	Free-text description of a comorbidity, as recorded in the source system, before mapping to controlled vocabularies.
measurement_source_text	Free-text representation of a measurement, observation, or test, as originally recorded in the source.
measurement_unit_source_text	Free-text representation of the unit of measurement as originally recorded in the source system, prior to mapping to a standardized unit ontology (e.g., UO or UCUM). This preserves verbatim units provided by labs or instruments.
exposure_source_text	Free-text description of an exposure (e.g., environmental, occupational), prior to mapping to ontology terms.
specimen_tissue_source_text	Free-text description of the tissue source for a specimen, as captured in the source system.
specimen_anatomic_location_source_text	Free-text description of the anatomical location of specimen collection, prior to ontology coding.
molecular_type_source_text	Free-text description of the molecular analyte type (e.g., DNA, RNA, protein) as captured in the source record.
assay_type_source_text	Free-text description of the assay type used, as originally recorded in the source system.
instrument_source_text	Free-text description of the sequencing instrument or platform as originally recorded in the source, prior to ontology mapping.
library_layout_source_text	Free-text description of the sequencing library layout as originally recorded in the source system.