Improve ZIP code handling

[nikhilwoodruff]

cc @MaxGhenis

This PR changes the automatic zip code handling, which can cause large fluctuations in MTR charts.

Current logic: ZIP codes are randomly sampled from the entire US for every household in the simulation (including axis variation households.

New logic:

• For axes-containing simulations: ZIP code is sampled from the household's state and repeated for all households (in that state).
• For other simulations: ZIP code is sampled from the household's state.

🤖 Generated by Copilot at ce77ab1

Summary

📝🐛🗺️

This pull request fixes a bug in the zip_code variable formula that caused inconsistent and random zip codes for households. It also updates the changelog entry to reflect the bug fix and the minor version bump.

zip_code formula
changed to match state and axes
fall leaves no errors

Walkthrough

• Update changelog entry to reflect minor version bump and bug fix (link)
• Fix zip code sampling logic to match state code and handle axes (link)

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (67e95c7) 99.02% compared to head (33d86b2) 99.01%.
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3227      +/-   ##
==========================================
- Coverage   99.02%   99.01%   -0.02%     
==========================================
  Files        1798     1798              
  Lines       26614    26621       +7     
  Branches      155      158       +3     
==========================================
+ Hits        26354    26358       +4     
- Misses        223      225       +2     
- Partials       37       38       +1     

Files	Coverage Δ
...sehold/demographic/geographic/zip_code/zip_code.py	82.35% <66.66%> (-17.65%)	⬇️

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[nikhilwoodruff]

Tests passing locally, merging.