Add Arizona Child Care Assistance Program

[hua7450]

Summary

Fixes #8370.

Adds Arizona's Child Care Assistance Program (CCAP), including:

• Eligibility for Arizona families with an eligible child under age 13.
• Initial and ongoing income eligibility using the DES FFY 2026 fee schedule.
• az_ccap_enrolled to apply ongoing/redetermination eligibility through 85% SMI.
• DES daily copays by fee level, with formula-based copay exemptions for TANF enrollment, protective services, and foster care pathways.
• DES reimbursement rates by provider type, child age group, quality status, formula-derived special-needs child status, and school-age season.
• Monthly subsidy calculation as max(0, min(pre-subsidy childcare expenses, state maximum reimbursement) - copay).

Regulatory Authority

• Arizona DES child care assistance eligibility page.
• DES CCA-0229A, Child Care Assistance Gross Monthly Income Eligibility Chart and Fee Schedule FFY 2026.
• DES CCA-1227A, Maximum Reimbursement Rates for Child Care, effective November 1, 2025.
• Arizona Administrative Code Title 6, Chapter 5, Article 49.
• DES Child Care Provider Registration Agreement CCA-1210B for special-needs definition and enhanced-rate criteria.

Income Eligibility Tests

• Non-enrolled applicants use fee levels L1-L6, corresponding to the initial 165% FPL limit.
• Enrolled recipients use az_ccap_enrolled and may qualify through fee level L7, corresponding to the ongoing 85% SMI limit.
• Family sizes 1-12 use the DES FFY 2026 monthly gross income thresholds.

Income Deductions And Exemptions

• Countable income uses observed PolicyEngine income variables matching R6-5-4914 countable income categories.
• Excluded income is handled by omission from the countable income source list.

Standards And Benefit Calculation

• Copay is a daily per-child amount by fee level and attendance days.
• az_ccap_copay_exempt is formula-based from is_tanf_enrolled, receives_or_needs_protective_services, and is_in_foster_care.
• az_ccap_special_needs_child is formula-based from eligible child status and is_disabled.
• Reimbursement uses provider type, child age group, school-age season, quality enhanced rate, and special-needs rate.
• CDA-only enhanced rates and TCC third-child copay cap are intentionally excluded by scope decision.

Requirements Coverage

• Covered: Arizona residence, child age, activity proxy, initial and ongoing income limits, countable income sources, family-size thresholds, fee levels, daily copays, formula-based copay exemptions, provider/age/season rates, quality rate, formula-based special-needs rate, final subsidy formula, and CCDF/state-benefit aggregation.
• Out of scope by user decision: CDA-only enhanced rates and TCC no-copay-beyond-third-child rule.
• Not modeled: waiting lists, verification workflow, provider contract status, nonpayment sanctions, overpayments, appeals, exact administrative notices, time limits, and child citizenship/qualified noncitizen verification.

Files Added

• policyengine_us/parameters/gov/states/az/hhs/ccap/...
• policyengine_us/variables/gov/states/az/hhs/ccap/...
• policyengine_us/variables/gov/states/az/hhs/az_child_care_subsidies.py
• policyengine_us/tests/policy/baseline/gov/states/az/hhs/ccap/...
• sources/working_references.md
• changelog.d/added/8370.md

Validation

• policyengine-core test policyengine_us/tests/policy/baseline/gov/states/az/hhs/ccap -c policyengine_us
• make format

Known failing tests: none.

[codecov]

Codecov Report

❌ Patch coverage is 74.68880% with 61 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.42%. Comparing base (92fdab8) to head (04d7239).
⚠️ Report is 13 commits behind head on main.

Files with missing lines	Patch %	Lines
...ables/gov/states/az/hhs/ccap/az_ccap_daily_rate.py	55.00%	9 Missing ⚠️
.../variables/gov/states/az/hhs/ccap/az_ccap_copay.py	58.82%	7 Missing ⚠️
.../hhs/ccap/eligibility/az_ccap_activity_eligible.py	56.25%	7 Missing ⚠️
...iables/gov/states/az/hhs/ccap/az_ccap_age_group.py	77.27%	5 Missing ⚠️
...les/gov/states/az/hhs/ccap/az_ccap_copay_exempt.py	64.28%	5 Missing ⚠️
...states/az/hhs/ccap/eligibility/az_ccap_eligible.py	64.28%	5 Missing ⚠️
...gov/states/az/hhs/ccap/income/az_ccap_fee_level.py	64.28%	5 Missing ⚠️
.../states/az/hhs/ccap/income/az_ccap_income_limit.py	66.66%	5 Missing ⚠️
...ine_us/variables/gov/states/az/hhs/ccap/az_ccap.py	71.42%	4 Missing ⚠️
.../az/hhs/ccap/eligibility/az_ccap_eligible_child.py	69.23%	4 Missing ⚠️
... and 3 more

Additional details and impacted files

@@             Coverage Diff              @@
##              main    #8373       +/-   ##
============================================
- Coverage   100.00%   70.42%   -29.58%     
============================================
  Files            2     4837     +4835     
  Lines           57    70490    +70433     
  Branches         1      346      +345     
============================================
+ Hits            57    49645    +49588     
- Misses           0    20843    +20843     
- Partials         0        2        +2     

Flag	Coverage Δ
unittests	70.42% <74.68%> (-29.58%)	⬇️

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