Added scripts/corpus_1000/demand_cohort.py (isolates fabric/demand-driven
divergences from cost noise). Investigation conclusion: the demand-side tail is
one-offs, not a cluster. 12109191 (+13.1) is a LODGED decimal error (365.67 m²
floor, 10x its ground floor). 217060420 (-4.4) is spec-faithful (36.6 m2 lodged
glazing at spec U). The only >=3 structural clusters among diverging certs are
electric flats (already diagnosed spec-faithful). No generic fabric bug remains;
gauge 77.7% is near its structural ceiling. Marked 12109191 unbuildable in ledger.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
