Medicaid CE: model 1115 comparable adult populations in scope

[daphnehanse11]

Parent issue: #7751

PR #8257 scopes Medicaid community engagement requirements to the modeled ACA adult Medicaid category. CMS guidance also discusses section 1115 demonstration populations with benefit packages comparable to minimum essential coverage. PolicyEngine currently does not appear to identify those populations separately.

Scope:

• Confirm the exact CMS standard for 1115 demonstration populations subject to community engagement.
• Inventory current state-specific Medicaid waiver or expansion variables that could represent these groups.
• Add a focused applicability variable, for example is_medicaid_ce_applicable_adult, that can combine the ACA adult category with any modeled 1115-equivalent adult groups.
• Add tests showing ordinary parent, child, pregnant, SSI, and senior or disabled categories remain outside the requirement unless separately included by the applicability variable.

Out of scope:

• Monthly compliance or lookback logic.
• Modeling every 1115 waiver population before any state has a clear PolicyEngine variable for it.

Sources:

• https://www.congress.gov/bill/119th-congress/house-bill/1/text
• https://www.medicaid.gov/federal-policy-guidance/downloads/cib12082025.pdf