Maine Sales Tax Fairness Credit (STFC) parameters missing 2025 update (skipped in PR #7384)

[PavelMakarchuk]

Summary

me_sales_tax_fairness_credit returns 2024 values for tax year 2025 because PR #7384 ("Update Maine income tax parameters for 2025") updated PTFC and other ME parameters but skipped the STFC. The legal values for 2025 are published in the 2025 Schedule PTFC/STFC (page 4 instructions).

Tracking issue from policyengine-taxsim: PolicyEngine/policyengine-taxsim#873

Required 2025 parameter updates

In policyengine_us/parameters/gov/states/me/tax/income/credits/fairness/sales_tax/:

amount/base.yaml — add 2025-01-01 values:

Filing status	2024 (current)	2025 (correct)
SINGLE	$150	$155
JOINT, SURVIVING_SPOUSE	$210	$220
HEAD_OF_HOUSEHOLD	$210	$220

reduction/start.yaml — add 2025-01-01 values:

Filing status	2024 (current)	2025 (correct)
SINGLE	$24,750	$25,450
HEAD_OF_HOUSEHOLD	$37,100	$38,200
JOINT, SURVIVING_SPOUSE	$49,500	$50,950

The reduction.increment ($1,000) and reduction.amount ($10/$15/$20 by filing status) match the form table's $20-per-$1,000 step for joint filers and don't need changes.

The additional per-child amounts (joint: $30 at 1 dep, $60 at 2+; HoH: $30 at 2, $60 at 3+; surviving spouse: $30 at 1, $60 at 2+) also still match the 2025 table maxima ($220 base + $60 = $280 max).

Reproducing case (from taxsim #873)

Joint, both age 40, $20K spouse wages, $881 interest, $31,749 SS, 2 kids (ages 2 and 11), $30K property tax, $20K mortgage. Federal AGI $23,259; ME total income (Schedule PTFC/STFC line 3) = $52,630.

	Value	Computation
Current PE	$190	max ($210+$60) − ceil((52,630−$49,500)/$1,000) × $20 = $270 − $80
Expected (2025 form table)	$240	max ($220+$60) − ceil((52,630−$50,950)/$1,000) × $20 = $280 − $40

Integration test

Append to policyengine_us/tests/policy/baseline/gov/states/me/tax/income/credits/fairness/sales_tax_fairness_credit/me_sales_tax_fairness_credit.yaml:

- name: 2025 ME STFC matches Schedule PTFC/STFC line 17 table for MFJ with 2 deps at income ~$52.6K
  period: 2025
  absolute_error_margin: 1
  input:
    people:
      head:
        age: 40
        taxable_interest_income: 881.35
        social_security: 31749.33
        real_estate_taxes: 30000
        deductible_mortgage_interest: 20000
      spouse:
        age: 40
        employment_income: 20000
      k1: {age: 11}
      k2: {age: 2}
    tax_units:
      tu: {members: [head, spouse, k1, k2]}
    households:
      hh: {members: [head, spouse, k1, k2], state_fips: 23}
  output:
    me_sales_tax_fairness_credit: 240