Adds scripts/fetch_cohort2_api_jsons.py (throwaway one-off) plus 38
golden fixtures under domain/sap10_calculator/rdsap/tests/fixtures/golden/
covering every cert in "sap worksheets/additional with api 2/".
Each JSON is the inner `data` payload from the gov.uk EPB
/api/certificate endpoint — the same shape EpcPropertyDataMapper
.from_api_response consumes today.
Required prerequisite for Slice B (parametrized API-path chain test
that mirrors the cohort-2 Summary-path sweep at 1e-4 vs worksheet).
Per the cross-mapper-parity primitive: API EPC and Elmhurst EPC must
produce SAP within 1e-4 of each other and of the worksheet — the SAP
cascade is the load-bearing equivalence check.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
