Update Illinois 2025 state tax code

[daphnehanse11]

Fixes #7224

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.09%. Comparing base (60c5dcc) to head (007a8e9).
⚠️ Report is 172 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7226      +/-   ##
==========================================
+ Coverage   73.76%   75.09%   +1.32%     
==========================================
  Files        3666     3666              
  Lines       52712    52710       -2     
  Branches      263      263              
==========================================
+ Hits        38882    39581     +699     
+ Misses      13815    13091     -724     
- Partials       15       38      +23     

Flag	Coverage Δ
unittests	75.09% <ø> (+1.32%)	⬆️

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[DTrim99]

PR Review

✅ Overall Assessment: APPROVE

This PR correctly updates Illinois income tax parameters for 2025. The core values have been verified against official Illinois Department of Revenue sources.

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🟢 Validated (No Critical Issues)

Check	Result
Regulatory Accuracy	✅ Verified - $2,850 exemption values match IL-1040 Instructions
Parameter Values	✅ Correct format (2_850), proper dates (2025-01-01)
YAML Structure	✅ Well-formed, all required metadata present
CI Status	✅ All checks passing
Changelog	✅ Present and descriptive

Key Verified Values:

• Personal exemption 2025: $2,850 ✓ (verified from IL-1040 Instructions page 8)
• Dependent exemption 2025: $2,850 ✓ (verified from Schedule IL-E/EIC)
• Increase from 2024: $75 (~2.7% COLA), rounded to nearest $25 per uprating config

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🟢 Positive Changes

1. Chronological reference ordering - References now organized oldest-to-newest (improved readability)
2. Typo fix - "EITC" corrected to "EIC" in schedule reference titles
3. Whitespace cleanup - Trailing whitespace removed in several files
4. URL updates - Year-specific URLs (/2024/) used for archived years, currentyear appropriately used for 2025

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🟡 Minor Observations (Non-blocking)

1. Some historical reference URLs may be broken - Illinois Department of Revenue appears to only archive instruction PDFs (il-1040-instr.pdf), not form PDFs or schedules. This is a pre-existing issue affecting many IL parameter files, not introduced by this PR. The statutory citations (35 ILCS) remain valid.

2. Test coverage - No 2025-specific tests included. While not strictly required for parameter-only changes (formulas are unchanged), adding 2025 test cases would provide additional validation:

   # Example for il_dependent_exemption.yaml
   - name: Two dependents in 2025
     period: 2025
     input:
       tax_unit_dependents: 2
       state_code: IL
     output:
       il_dependent_exemption: 5_700  # 2 × $2,850

3. Reference title inconsistency - 2025 references use "Illinois Department of Revenue" prefix while some earlier years omit it. Cosmetic only.

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📋 Files Modified (13)

Category	Files
Exemptions	dependent.yaml ⭐, personal.yaml ⭐, aged_and_blind.yaml, income_limit.yaml
Credits	ctc/age_limit.yaml, ctc/rate.yaml, eitc/match.yaml, k12/cap.yaml, k12/rate.yaml, k12/reduction.yaml, property_tax/rate.yaml
Tax Rate	rate.yaml
Changelog	changelog_entry.yaml

⭐ = Contains new 2025 parameter values

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✅ Recommendation: Merge

The parameter values are accurate and verified against official sources. This PR is ready for merge.

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