Add Trump dividend contributed reform

[DTrim99]

Summary

Adds a contributed reform modeling a "Trump dividend": a $5,000 payment to each citizen aged 18 and older. Inert in baseline — activated by setting gov.contrib.trump.dividend.in_effect to true (e.g., for tax year 2027).

Why a new reform instead of adjusting existing parameters

• American Worker Rebate Act (Hawley tariff rebate): pays per filing unit, and the child amount reuses the same non_joint parameter, so a $5,000 setting would also pay every CTC-qualifying child. Includes LPRs and misses adult dependents.
• Recovery rebate credit (stimulus checks): eligibility keys on valid SSN rather than citizenship, and adult dependents (neither head nor spouse) would receive nothing.
• UBI Center basic income: supports per-person age-bracketed amounts but has no citizenship gating.

Design decisions

• Provenance: hypothetical illustrative parameters — no official source document exists; the parameter files note this explicitly.
• Taxability: the payment is intentionally non-taxable (excluded from AGI and MAGI bases), matching basic_income's default treatment; a taxable toggle can be added later if needed.
• Means-tested interactions: the payment deliberately does not enter SNAP or SSI countable income, matching the basic_income precedent.
• Microsim note: immigration_status defaults to CITIZEN in the microdata, so population runs treat nearly all adults as eligible, overstating cost by roughly the non-citizen adult share.

Implementation

• Parameters under gov/contrib/trump/dividend/: amount ($5,000), min_age (18), eligible_immigration_statuses ([CITIZEN]), in_effect (false by default)
• Person-level trump_dividend_eligible and trump_dividend variables
• Flows into spm_unit_benefits and the household_benefits parameter list via the same channel as basic_income; non-taxable
• Six YAML tests covering the age boundary (17/18), citizenship gating, mixed households, and baseline inertness

🤖 Generated with Claude Code

https://claude.ai/code/session_01LqCGPgxDukji8Bhs57c5rH

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.68%. Comparing base (f9b5549) to head (3893625).
⚠️ Report is 57 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
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- Coverage   100.00%   92.68%   -7.32%     
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  Files            2        3       +1     
  Lines           20       41      +21     
  Branches         0        3       +3     
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+ Hits            20       38      +18     
- Misses           0        1       +1     
- Partials         0        2       +2     

Flag	Coverage Δ
unittests	92.68% <100.00%> (-7.32%)	⬇️

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