Net spouses' self-employment losses in state EITC helper earned income (IL, CO, DC, IN)

[PavelMakarchuk]

Fixes #9819.

Change

• calculate_eitc_amount_from_parameters (policyengine_us/tools/state_eitc_helpers.py) now uses eitc_earned_income instead of filer_adjusted_earnings. This is the same earned income as the federal eitc_phased_in and eitc_reduction (Fix EITC earned income self-employment netting #8337). It combines both spouses' wages and net self-employment earnings and floors only the total, per Form 1040 EIC Worksheet B.
• The Indiana decoupled branch of in_eitc (2011–2022) gets the same change.

The helper feeds il_eitc, co_eitc (ITIN and under-25 paths), dc_eitc_with_qualifying_child and in_eitc_eligible. The Washington credit imports other helper functions, not this one.

Tests

• Four existing cases set filer_adjusted_earnings as an input. They now set eitc_earned_income with the same value and keep the same outputs.
• Seven new cases have a joint return where one spouse has a self-employment loss. The expected values are TAXSIM-35 outputs for the same households (v39):

Test	Year	Expected	TAXSIM v39
IL, 2 children, wages 10,000, spouse SE −4,000	2021	432	432
same	2023	480	480
IL 65+ couple, wages 7,000, SE −2,000	2023	76.50	76.50
CO under-25 couple, no children, wages 10,000, SE −4,000	2023	229.50	229.50
DC, 1 child, wages 10,000, SE −4,000	2023	1,428	1,428
IN, 2 children, wages 10,000, SE −4,000	2022	240	240
same	2021	216	216

Before this change, PE gave 720, 800, 107.10, 300, 2,380, 400 and 360.

Local runs: the IL, CO credit, DC, IN, WA and federal EITC test folders pass (2,218 tests).

Census effect

In the TAXSIM-35 census comparison for IL, CO, DC and IN (2021–2025), 15 household-years change, 12 now match TAXSIM, and none that matched before stop matching. The other 3 are 2021 Illinois households that still differ by the Illinois rebate.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (909176a) to head (6232ba0).
⚠️ Report is 311 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #9820   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            4         1    -3     
  Lines           76        40   -36     
  Branches         2         3    +1     
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- Hits            76        40   -36     

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[hua7450]

Reviewed 03e3718. No calculation defect found in the static review: netting both spouses' wages and self-employment earnings before flooring the tax-unit total matches the IRS EIC Worksheet B treatment. I traced the helper's Illinois, Colorado, DC and Indiana callers, including Indiana's separate 2011–2022 calculation.

• Please add the required axiom: parity declaration to the PR description, following CLAUDE.md's Axiom Parity section.
• Optional regression coverage: add a spousal self-employment loss case in the state-credit phase-out range. The new cases primarily exercise phase-in and maximum-credit behavior.

Verification limits: I did not independently run the tests. All 37 check runs on this commit are successful as of October 6, 02:40 UTC. The source audit is partial: IRS and DC material was accessible, but some historical Illinois, Colorado and Indiana primary documents could not be retrieved.

[PavelMakarchuk]

Thanks. Merged main (both sides had appended cases to co_eitc.yaml and il_eitc.yaml; kept both) and added the phase-out range case you suggested:

• Illinois 2023, joint, two children, head wages 40,000, spouse self-employment loss 5,000. Earned income and AGI are 35,000, above the 28,120 joint phase-out start (Rev. Proc. 2022-38, section 3.06). Federal EITC 6,604 − 0.2106 × 6,880 = 5,155.07; IL EIC 20% = 1,031.01. Without netting the old helper gives 820.41 (earned income 40,000). It fails on main and passes here.

The IL, CO, DC and IN tests pass (2,442). I will add the axiom: line separately.