Joins each computed cert's signed error (eval _results.csv) with a rich
feature set extracted from its RAW API JSON (not the mapped
EpcPropertyData), then ranks (feature, value) buckets by error carried
and by |mean signed| bias. Surfaces systematic API-path handling gaps —
a field the mapper silently drops still shows as an error-correlated
bucket. Companion to eval_api_sap_accuracy.py / decompose_api_cost_error.py.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
