Add ACA subsidy-depth targets beyond enrollment and APTC people

Context

The current healthcare target surface covers ACA Marketplace enrollment and APTC recipients, and related open issues track ACA take-up/plan-choice work:

• #70 investigates ACA take-up and plan-choice inputs.
• #74 covers Marketplace take-up materialization.
• #75 covers selected-plan benchmark ratios and metal-level diagnostics.
• #168 covers joint calibration to CMS APTC people and SOI PTC returns/amounts.

Those issues do not fully track the remaining ACA subsidy-depth target surface: CSR recipients, metal tier beyond the current bronze diagnostic, income band, gross premiums, and net premiums where source artifacts expose them.

Goal

Add ACA subsidy-depth targets/diagnostics so healthcare release comparisons can show not just who is in Marketplace coverage, but how subsidized and what kind of coverage they have.

Suggested implementation

• Inventory CMS OEP/effectuated-enrollment artifacts already available to Ledger/Populace for:
  • CSR recipients
  • metal tier
  • income band
  • gross premiums
  • net premiums after subsidies
• Add target roles for feasible hard targets and diagnostics for source facts that are not yet safe to calibrate against.
• Keep these roles distinct from aca_enrollment, aca_ptc_recipients, aca_spending, and existing bronze/benchmark-ratio diagnostics.
• Where possible, expose national and state-level target tables.

Acceptance criteria

• Release artifacts expose which ACA subsidy-depth targets are available and which are intentionally absent.
• Tests cover target mapping for each supported subsidy-depth source concept.
• Healthcare diagnostics can compare release-over-release fit for subsidy depth without conflating it with total Marketplace enrollment.
• Existing ACA issues (#70, #74, #75, #168) link to this issue when their implementation depends on these target surfaces.

Start by inventorying the CMS OEP and effectuated-enrollment artifacts already available to Ledger/Populace, then inspect existing ACA target roles and diagnostics. Map each supported concept—CSR recipients, metal tier, income band, gross premiums, and net premiums—to target or diagnostic coverage, and add tests for the mappings. Done means release artifacts clearly show supported and intentionally absent targets, with subsidy-depth comparisons kept separate from enrollment.