PGx: ClinPGx variant-based genes (PGX-008) and --guideline dpwg (PGX-025)

- fetch_sources.sh downloads ClinPGx clinicalVariants (CC BY-SA 4.0); pgx db build adds genotype-only
  variant-based genes (levels 1A-2B, level 3 for the parity list), rsIDs resolved from the manifest's probes:
  70 genes in the DB.
- pgx phenotype --guideline dpwg: CPIC mappings for CPIC genes (as ClinPGx curates DPWG), no phenotype for
  DPWG-only genes (flags dpwg_via_cpic_mapping / dpwg_mapping_not_available). K-029 updated.

docs/validation/V2_pgx_star.md

@@ -92,4 +92,12 @@ so the per-call error is 1e-3 (GS ≥ 0.15) and errors are handled by the probe
   from the GRCh38 haplotype VCFs, `*1` = reference, prior reference 0.8 (no population frequencies); genotype only
   (no CPIC phenotype). The probe mask was re-derived with these variants (one more record: CYP2A6 19:40843845 C>A,
   concordance 0.47, which had produced false *5 calls).
-* Not yet: DPWG tables.
+* ClinPGx clinical-annotation variants (CC BY-SA 4.0; levels 1A–2B, and level 3 for the PGX-008 parity genes) add
+  genotype-only variant-based genes — OPRM1, COMT, DRD2, ANKK1, MTHFR, F5, … (43 genes, 171 of 187 rsIDs resolved on
+  GSA v4 PGx from the manifest's probes). The DB now holds 70 genes (16 star-allele, G6PD, 2 HLA tag, 51
+  variant-based; spec parity list: 58). `pgx coverage`: 1225 alleles callable, 93 array-equivalent, 437 not
+  covered, 5 masked.
+* `--guideline dpwg` (PGX-025): ClinPGx curates DPWG guidelines with the CPIC allele-function and phenotype mappings
+  for genes CPIC covers, so those genes reuse the CPIC tables (flag `dpwg_via_cpic_mapping`); DPWG-only genes
+  (CYP1A2, CYP3A4, F5) have no public machine-readable mapping and get phenotype `null` with the flag
+  `dpwg_mapping_not_available` (K-029).