Restore medical_out_of_pocket_expenses as deprecated alias

[hua7450]

Summary

PR #8178 (shipped in policyengine-us 1.673.0) removed the umbrella medical_out_of_pocket_expenses Person variable in favor of program-specific aggregates (itemized_medical_expenses, snap_allowable_medical_expenses, hud_medical_expenses, medicaid_medically_needy_medical_expenses, pa_ccw_medical_expenses) plus decomposed inputs (health_insurance_premiums, other_medical_expenses, over_the_counter_health_expenses, medicare_part_b_premium, ...).

Household-API partners that still pass medical_out_of_pocket_expenses as input now hit VariableNotFoundError (HTTP 500) without prior notice — see PolicyEngine/policyengine-household-api#1493 for the MyFriendBen fixture migration that surfaced this.

This PR re-adds medical_out_of_pocket_expenses as a deprecation alias that forwards into other_medical_expenses, giving partners a window to migrate.

Approach

• New Person-level input variable medical_out_of_pocket_expenses (default 0). Label and documentation mark it deprecated.
• other_medical_expenses now declares adds = [\"medical_out_of_pocket_expenses\"]. PolicyEngine input-override semantics mean partners who already pass other_medical_expenses (or the new premium inputs) directly are unaffected — direct input always wins over adds. Pattern matches existing variables that combine uprating and adds (e.g. employment_income, self_employment_income).

Tradeoff

This is an alias to other_medical_expenses only — the non-premium catch-all. For partners whose legacy medical_out_of_pocket_expenses value previously included health insurance premiums, the shim silently routes those dollars into the non-premium path; they will need to migrate that portion to health_insurance_premiums to retain correct downstream calculations. Of the three customer-input fixtures in policyengine-household-api (my_friend_ben, amplifi, impactica), only MyFriendBen passed the legacy variable, and they don't pass any premium inputs — so the simple alias is correct for them.

Removal plan

The shim is a temporary migration aid. We should track its removal as a follow-up issue and pull it after partners have had at least one minor-version cycle to migrate.

Files

• policyengine_us/variables/household/expense/health/medical_out_of_pocket_expenses.py (new)
• policyengine_us/variables/household/expense/health/other_medical_expenses.py (modified)
• policyengine_us/tests/policy/baseline/household/expense/health/medical_out_of_pocket_expenses.yaml (new)
• changelog.d/restore-medical-oop-expenses-alias.added.md (new)

Test plan

• YAML test verifies legacy input flows into other_medical_expenses
• YAML test verifies direct other_medical_expenses input overrides the alias
• YAML test verifies default-zero behavior when neither input is supplied
• CI passes

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (623a65c) to head (0a72f97).
⚠️ Report is 134 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%            
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  Files           12         2    -10     
  Lines          173        17   -156     
  Branches         4         0     -4     
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- Hits           173        17   -156     

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unittests	100.00% <100.00%> (ø)

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