Add CHIP current-coverage input for CPS/API partner data

[daphnehanse11]

Context

The CHIP calibration starter PR in policyengine-us-data, PolicyEngine/policyengine-us-data#1162, uses CPS NOW_PCHIP as reported_has_chip_health_coverage_at_interview to anchor takes_up_chip_if_eligible and calibrate CHIP enrollment targets.

PolicyEngine-US already has the core CHIP rules variables:

• takes_up_chip_if_eligible
• chip_enrolled

But it does not appear to expose a CHIP-specific current coverage input analogous to existing inputs such as:

• has_medicaid_health_coverage_at_interview
• has_marketplace_health_coverage_at_interview
• has_other_means_tested_health_coverage_at_interview

That leaves CHIP reported-current-coverage data as a data-package-only column rather than a rules/API input that partners can pass explicitly.

Proposed change

Add a US rules variable:

• has_chip_health_coverage_at_interview
  • entity: Person
  • value type: bool
  • definition period: YEAR
  • label along the lines of Person currently has CHIP health coverage

Then wire it consistently with the existing current-coverage inputs.

Acceptance criteria

• Add has_chip_health_coverage_at_interview under the household health coverage input variables.
• Include CHIP in current qualifying non-marketplace coverage counts if that matches the intended ACA/MEC treatment.
• Add baseline tests showing the input is accepted and contributes to the relevant current-coverage aggregation/conflict logic.
• After this lands, update policyengine-us-data#1162 or a follow-up us-data PR to populate this rules input from CPS NOW_PCHIP, while preserving any raw reported field if useful for source diagnostics.

Related

• Add CHIP enrollment calibration targets policyengine-us-data#1162
• Calibrate CHIP take-up before estimating premium collections #8523