Add historical TANF parameter data (pre-2018) for DE, MO, PA, RI, SD

[hua7450]

Summary

Fixes #7169

Adds historical TANF parameter data (pre-2018) for five states and implements Pennsylvania's Work Expense Reimbursement (WER) mechanism for the 2009-2020 period.

Changes

Historical Parameter Updates

State	Parameter	Old Start	New Start	Notes
DE	deficit_rate	2024-10-01	2011-10-01	50% deficit rate per 2011 State Plan
MO	minimum_payment	2024-01-01	2002-01-01	$10 rule from 1948 AFDC (13 CSR 40-2.120)
RI	dependent_care/amount	2019-01-01	2008-07-01	Rhode Island Works inception
SD	max_table_size	2023-07-01	2016-09-01	Matches other payment standard files

Pennsylvania Work Expense Restructure

Added support for two distinct work expense mechanisms:

Work Expense Reimbursement (WER) - 2009-2020:

• $50/month flat bonus added to TANF benefit
• Paid to families with earned income

Work Expense Deduction (WED) - 2020+:

• $200/month deducted from countable earned income
• Applied after 50% earned income disregard

New parameter structure:

pa/dhs/tanf/income/work_expense/
├── uses_deduction.yaml    # false (2009) → true (2020)
├── deduction.yaml         # $200 WED amount
└── reimbursement.yaml     # $50 WER amount

References

• PA DHS Cash Assistance Handbook Section 137.4 (WER)
• PA DHS TANF State Plan 2024 (WED)
• 13 CSR 40-2.120 - Missouri minimum payment
• Delaware TANF State Plan 2011
• R.I. Gen. Laws Chapter 40-5.2 - Rhode Island Works Act of 2008
• ARSD 67:10:05:03 - South Dakota Payment Standards (2016)

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (f506aab) to head (d23880e).
⚠️ Report is 15 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files            2         2           
  Lines           32        36    +4     
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+ Hits            32        36    +4     

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

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