Add ZIP code-level HUD payment standards for Texas and Kansas

[hua7450]

Summary

Resolves Housing Choice Voucher (HCV) payment standards at the ZIP-code level for Texas and Kansas, replacing the county-level Fair Market Rent where finer data exists (~1,059 covered ZIPs). Previously pha_payment_standard only varied by county (plus a hardcoded LA County schedule).

• Texas — published PHA schedules (TDHCA + Houston HHA) plus HUD Small Area FMRs for the 4 mandatory-SAFMR metros.
• Kansas — HUD Small Area FMRs for the 2 mandatory-SAFMR metros only (Kansas has no statewide PHA schedule to adopt), with the county FMR elsewhere.

How

pha_payment_standard resolves from most to least geographically specific:

1. Published ZIP payment standard — zip_code_payment_standard (a PHA's actually-adopted schedule)
2. Metro Small Area FMR — small_area_fair_market_rent, used only where safmr_used_for_hcv is true (a mandatory-SAFMR metro)
3. LA County local schedule — unchanged
4. County FMR — hud_fair_market_rent, unchanged

ZIP paths only fire on a match, so county-level and microsimulation households (where zip_code is unset) are unaffected. Where a ZIP has both a published standard and a SAFMR, the published standard wins.

Data

State	Source	Coverage	Bedrooms	Year
TX	TDHCA published HCV payment standards	284 ZIPs / 34 counties	0–6	2025
TX	Houston Housing Authority (HHA) published standards	146 ZIPs (tiered A/B/C/D)	0–6	2025
TX	HUD Small Area FMRs (Beaumont-Port Arthur, Dallas, Fort Worth-Arlington, San Antonio-New Braunfels)	550 ZIPs	0–4	FY2026
KS	HUD Small Area FMRs (Kansas City, MO-KS [KS side] and Wichita, KS)	174 ZIPs (91 + 83)	0–4	FY2026

TX published standards total 430 ZIPs (284 TDHCA + 146 HHA); TX combined distinct coverage is 885 ZIPs. Adding Kansas's 174 SAFMR ZIPs gives ~1,059 distinct covered ZIPs. The SAFMR table now holds 724 ZIPs across 6 metros.

hud_area_name in small_area_fair_market_rents.csv is suffixed with the 2-letter state (e.g. Dallas, TX, Wichita, KS) so metros read unambiguously across states; the bi-state Kansas City metro's KS-side rows are labeled Kansas City, KS.

• Published standards: parameters/gov/hud/payment_standards/zip_code_payment_standards.csv
• SAFMR: parameters/gov/hud/fmr/small_area_fair_market_rents.csv

Variables

• Filled small_area_fair_market_rent (ZIP→SAFMR lookup) and safmr_used_for_hcv (designated-metro gate)
• Added zip_code_payment_standard (ZIP→published-standard lookup)
• Rewired pha_payment_standard

This also activates the Harris Rent Relief Act contrib reform's SAFMR-based rent cap for the covered metros — it consumes small_area_fair_market_rent / safmr_used_for_hcv, which were previously stubs (see the changed changelog fragment).

Notes / limitations

• Coverage is where ZIP-level rent data exists (published PHA schedules + mandatory-SAFMR metros). Elsewhere (rural TX/KS, non-mandatory metros) the county FMR applies, matching HUD policy.
• Houston is not a mandatory-SAFMR metro (HUD publishes SAFMR data for it but does not mandate its use), so Houston ZIPs use HHA's adopted published standards, not SAFMR.
• Kansas is SAFMR-only. Kansas has no TDHCA-style statewide balance-of-state PHA (HCV is fragmented across ~23 local PHAs), so only the two mandatory-SAFMR metros are modeled. For the bi-state Kansas City metro, only the KS-side ZIPs are bundled. Wichita HA sets standards at 100% of SAFMR (so we match it exactly); the KCK hold-harmless floor and Johnson County's 90–110% tiering are not modeled (raw SAFMR is used there).
• small_area_fair_market_rent carries data only for the designated TX/KS metros (0 elsewhere), so the Harris reform's SAFMR-based rent cap is non-zero only there.
• Year labels follow the published data (published standards 2025, SAFMR FY2026); the framework imputes the nearest available year.

Verification

• TDHCA published standards (284 ZIPs × 7 bedrooms) re-extracted from the source PDF via two independent engines — 0 mismatches.
• Houston HHA standards (146 ZIPs × 7 bedrooms) transcribed from HHA's published payment-standard schedule (effective 2025-01-01).
• SAFMR (724 ZIPs × 5 bedrooms: 550 TX + 174 KS) extracted from HUD's FY2026 revised SAFMR file (fy2026_safmrs_revised.xlsx), filtered to the mandatory metros; the designated-metro set for both states verified against HUD's Designated SAFMR Areas list (Aug 2024). The bi-state Kansas City metro is filtered to KS-side ZIPs.
• pd.merge order-preservation confirmed on scrambled multi-household vectors; both ZIP merges now use validate="many_to_one".

Test plan

• Unit tests for small_area_fair_market_rent, zip_code_payment_standard, safmr_used_for_hcv, and precedence/state cases in pha_payment_standard (TX and KS, including Kansas City MO-side and Topeka exclusions)
• CI passes

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (9f9d644) to head (c7fcd4c).
⚠️ Report is 142 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files            2         4    +2     
  Lines           37        82   +45     
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+ Hits            37        82   +45     

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unittests	100.00% <100.00%> (ø)

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