dna-chip-coverage: SNP marker coverage across consumer DNA genotyping arrays

A per-marker, per-platform table of which clinically discussed SNP markers are carried by the genotyping arrays that consumer DNA tests are built on, derived from published array manifests, NCBI dbSNP, and openly published raw data files. Each call records the evidence it rests on, and states unknown where the public record does not settle the question rather than guessing. The repository includes notable-gaps.md, an analysis of cases where a reported result is structurally unsupported by the source array — for example an APOE ε genotype, which requires both rs429358 and rs7412, where all five arrays carry rs7412 and exactly one carries rs429358 — and scripts/build.py, which regenerates the table from the manifests from scratch. A manifest describes the array a product was built on, not what the product shipped, so manifest-derived calls are supplemented by observations from openly published raw data files — which is the only way custom vendor content becomes visible. Coverage of clinically relevant variants on genotyping arrays is an established subject and no finding here is claimed as novel; see the Prior work section of the README. What this provides is a machine-readable table with the source of every call.