[codex] Model Virginia Medicaid LIFC regional limits

[daphnehanse11]

Fixes #5798.

Summary

This models Virginia's Medicaid Low Income Families With Children (LIFC) regional income limits for parent/caretaker eligibility. Virginia's parent Medicaid limit is not a single statewide FPL percentage; DMAS publishes annual dollar limits by LIFC locality Group I, Group II, and Group III.

Changes

• Adds DMAS LIFC income-limit parameters effective July 1, 2025 for Groups I, II, and III, including additional-person amounts.
• Adds DMAS LIFC locality group parameters from Appendix 4.
• Adds va_medicaid_lifc_locality_group and va_medicaid_lifc_income_limit.
• Adds medicaid_parent_income_limit, so Virginia uses its regional LIFC limit while other states continue using the existing national parent Medicaid income-limit table.
• Updates parent Medicaid financial eligibility to treat income exactly at the applicable limit as eligible, matching DMAS language that income exceeding the LIFC limit is ineligible.

Sources

• Virginia Medical Assistance Eligibility Manual, Chapter M03: https://www.dmas.virginia.gov/media/ticpwqt4/m03-1-1-26.pdf#page=125
• Virginia Medical Assistance Eligibility Manual, Chapter M04 Appendix 3 and 4: https://www.dmas.virginia.gov/media/0aynyhxk/m04-1-1-26a.pdf#page=51
• Virginia Medical Assistance Eligibility Manual, Chapter M07: https://www.dmas.virginia.gov/media/xwseehc2/m07-7-1-25.pdf#page=8

Not Modeled

• Retroactive entitlement, Marketplace referrals, LIFC Extended Medicaid, and administrative processing.
• Full caretaker-relative relationship verification beyond the existing parent nonfinancial proxy.
• Historical regional income tables before the current DMAS manual.

Validation

• make format
• .venv/bin/policyengine-core test policyengine_us/tests/policy/baseline/gov/states/va/dmas/medicaid/lifc -c policyengine_us
• .venv/bin/policyengine-core test policyengine_us/tests/policy/baseline/gov/hhs/medicaid/eligibility/categories/parent/medicaid_parent_income_limit.yaml -c policyengine_us
• .venv/bin/policyengine-core test policyengine_us/tests/policy/baseline/gov/hhs/medicaid/eligibility/categories/is_parent_for_medicaid.yaml -c policyengine_us

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (ee131a9) to head (5110af7).
⚠️ Report is 23 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files            9         4    -5     
  Lines          149        64   -85     
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- Hits           149        64   -85     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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