Bump N_POSTCODES 150 -> 40 as the gradual-growth step from the 3-postcode
smoke. 40 postcodes / 1113 certs / 578 leave-one-out predictions is enough
for stable, trustworthy metrics (the smoke's 2 usable postcodes were
dominated by oddball flats — floor_area mean|.| 52.6 there vs 12.7 here).
Resumable + reproducible (random.seed(2026)); raise again to scale up.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Builds the frozen validation corpus: samples postcodes from the register, then
caches each postcode's full cohort of raw cert payloads (the shape
from_api_response consumes), grouped by postcode, resumably. Reads the token
from backend/.env; cache dir /tmp/epc_prediction_corpus (EPC_PREDICTION_CORPUS
override). IO plumbing, not test-driven. Pairs with the leave-one-out harness.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
