Changes in version 0.1.0                        

Initial release

  - audit_transformation() — main function to audit a full ZCTA → ZIP →
    County transformation pipeline and quantify perturbation.
  - transform_zcta_to_zip() — performs the first hop (ZCTA → ZIP) using
    equal-weight allocation across associated ZIPs.
  - transform_zip_to_county() — performs the second hop (ZIP → County)
    using HUD TOT_RATIO allocation.
  - run_full_transformation() — convenience wrapper executing both hops
    in sequence.
  - prep_zip_zcta() — standardizes raw ZIP-ZCTA crosswalk files for use
    in audits.
  - prep_hud_crosswalk() — standardizes raw HUD ZIP-County crosswalk
    files.
  - get_zcta_baseline() — fetches ACS 5-year estimates at ZCTA level via
    the Census API (requires tidycensus and a Census API key).
  - extract_perturbed_population() — extracts the redistribution of
    population across receiving counties produced by the transformation.
  - plot_transformation_perturbation() — bar chart of baseline vs
    recovered values with perturbation magnitude in subtitle.
  - create_audit_report() — generates all visualizations for an audit.
  - S3 print and summary methods for shellgame_audit objects.
  - Vignettes: Hennepin County worked example, data preparation guide,
    conceptual framework.