Finalize DTA LinkML model

[rchaitanyapradeep]

Feature: DTA Logical Data Model (LinkML)

Build a single LinkML schema that models the lab data transfer end to end and keeps
it traceable from USDM to SDTM-LB. It covers both senses of "DTA" — the Data Transfer
Agreement (the contract: what data, by whom, in what format, mapped to which
visits) and the lab Transmission payload (the data that fulfils it) — joined
through a shared BiomedicalConcept. The model is validated with linkml-validate
against representative pilot fixtures.

Tasks

• Define the schema (dta.linkml.yaml): agreement, semantic, and instance layers.
• Type the vocabularies as enums (units, file format, provenance, BC facets) and bind to CDISC CT / NCIt where known.
• Add example data files that pass validation: one Data Transfer Agreement and one lab results payload (using CDISC pilot study H2Q-MC-LZZT).
• Link the layers: BiomedicalConcept as the join, plus a reference from each Transmission to the Agreement it fulfils.
• Generate JSON Schema + Pydantic from the model and validate fixtures in CI.