Restructure EITC max to calculate from indexed earned income amounts

[MaxGhenis]

Current Implementation

EITC maximum credit amounts are stored as static values in gov/irs/credits/eitc/max.yaml with uprating metadata.

Ideal Implementation

Per IRC § 32, EITC max should be calculated as:

• EITC Max = credit percentage × earned income amount

Where:

• Credit percentages (IRC § 32(b)(1)): Fixed at 7.65%, 34%, 40%, 45% for 0, 1, 2, 3+ children
• Earned income amounts (IRC § 32(b)(2)(A)): Indexed annually with $10 rounding per IRC § 32(j)

Benefits

1. Matches statutory structure: Statute doesn't index EITC max directly, only the earned income amounts
2. Reduces manual maintenance: Only need to maintain earned income amounts, not calculated maxima
3. More accurate: Avoids rounding errors from uprating derived values
4. Clearer: Makes calculation transparent

References

• IRC § 32(b)(1) - Credit percentages
• IRC § 32(b)(2)(A) - Earned income amounts
• IRC § 32(j) - Inflation adjustments

Implementation

Would require creating variables that calculate EITC max from indexed parameters rather than reading directly from max.yaml.