Fix code bug in Illinois HBWD income

[hua7450]

Summary

Fixes #7165

Changes

1. Fix IL HBWD earned income exemptions (il_hbwd_countable_earned_income.py)

Per 89 Ill. Admin. Code § 120.510(i), earned income exemptions apply only to disabled/blind persons, not to all household members.

Before: All persons in the SPM unit received earned income exemptions (via il_aabd_earned_income_after_exemption_person), incorrectly reducing countable income for non-disabled spouses.

After: Only disabled/blind persons receive exemptions. Non-disabled/non-blind persons use gross earned income.

2. Add is_blind to disability eligibility (il_hbwd_disability_eligible.py)

SSA recognizes blindness as a category of disability (SSI has Aged, Blind, Disabled). Added is_blind check so blind workers qualify for HBWD.

3. Update il_hbwd_countable_income.py

Changed to use il_hbwd_countable_earned_income instead of il_aabd_earned_income_after_exemption_person.

Impact

Scenario 15 (from issue):

• Married couple: disabled worker ($4,500/month) + non-disabled spouse ($2,500/month)
• Combined gross: $7,000/month
• 350% FPL limit for 2 people: $6,168.75/month

Metric	Before (Bug)	After (Fixed)
Spouse exemptions	Yes (incorrect)	No
Countable income	~$5,770	~$6,323
Income eligible	Yes	No

Test Coverage

Added 17 new test cases covering:

• Single/married households
• Disabled/blind/non-disabled workers
• Age eligibility boundaries (under 16, over 64)
• Income at/above/below limits
• Families with children

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (f506aab) to head (8649b3a).
⚠️ Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #7166   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            2         3    +1     
  Lines           32        39    +7     
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+ Hits            32        39    +7     

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

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