Add Texas SSI state supplement

[MaxGhenis]

Summary

Implements the Texas Optional State Supplement (OSS) for SSI recipients in Medicaid-funded nursing facilities and ICF/IID facilities. Closes #7340.

Texas provides one of the most minimal SSI state supplements in the nation — available only to SSI recipients residing in Medicaid-funded long-term care facilities (nursing facilities and ICF/IID). The supplement brings the total personal spending money up to the state's Personal Needs Allowance (PNA).

Current benefit (2024+): $45/month ($540/year) per individual = $75 PNA - $30 federal reduced SSI

Regulatory authority

Authority	Citation
State PNA statute	Texas Human Resources Code § 32.024(w)
PNA increase to $75	HB 54, 88th Legislature (2023)
Federal reduced SSI benefit	42 USC § 1382(e)(1)(B)
HHSC PNA handbook	MEPD Handbook H-1500
HHSC co-payment rules	MEPD Handbook H-6000

Benefit calculation

State Supplement = max(0, Personal Needs Allowance - Federal Reduced SSI Benefit) × 12

Individual: ($75 - $30) × 12 = $540/year
Couple (both in facility): each person gets ($75 - $30) × 12 = $540/year

Historical PNA values

Period	PNA (monthly)	Supplement (monthly)
Sep 1999	$45	$15
Sep 2001	$60	$30
Sep 2003	$45	$15
Jan 2006	$60	$30
Jan 2024	$75	$45

Files added

Parameters (3):

• gov/states/tx/hhsc/ssi_state_supplement/personal_needs_allowance.yaml — TX PNA amount
• gov/ssa/ssi/amount/institutional/individual.yaml — Federal $30/month reduced SSI
• gov/ssa/ssi/amount/institutional/couple.yaml — Federal $60/month reduced SSI (couple)

Variables (3 new, 1 modified):

• gov/ssa/ssi/is_in_medicaid_facility.py — Federal input: whether person is in Medicaid facility
• gov/states/tx/hhsc/ssi_state_supplement/tx_ssi_state_supplement_eligible.py — Eligibility
• gov/states/tx/hhsc/ssi_state_supplement/tx_ssi_state_supplement.py — Benefit amount
• household/income/spm_unit/spm_unit_benefits.py — Added tx_ssi_state_supplement

Tests (3 files, 15 tests):

• tx_ssi_state_supplement_eligible.yaml — 4 unit tests (eligibility logic)
• tx_ssi_state_supplement.yaml — 3 unit tests (benefit amounts)
• integration.yaml — 8 integration tests (realistic scenarios including couples, historical periods, out-of-state)

Test plan

• All 15 YAML tests pass locally
• make format passes
• CI passes on GitHub

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.74%. Comparing base (a46b5a8) to head (45c786b).
⚠️ Report is 26 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7341      +/-   ##
==========================================
+ Coverage   86.56%   95.74%   +9.17%     
==========================================
  Files          12        4       -8     
  Lines         134       47      -87     
  Branches        0        2       +2     
==========================================
- Hits          116       45      -71     
+ Misses         18        1      -17     
- Partials        0        1       +1     

Flag	Coverage Δ
unittests	95.74% <100.00%> (+9.17%)	⬆️

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