| audit_transform | Audit a sequence of geographic transformations |
| clean_geo_headers | Normalize messy geography headers to standard names |
| prep_hud_crosswalk | Prepare HUD ZIP-to-County crosswalk |
| step_zcta_to_zip_equal | Step: ZCTA -> ZIP using equal-share allocation |
| step_zip_to_county_totratio | Step: ZIP -> COUNTY using HUD TOT_RATIO |