Assign data-construction inputs added by recent policyengine-us merges (SNAP ABAWD discretionary exemptions, CHIP take-up)

[MaxGhenis]

Summary

Recent policyengine-us merges added inputs that are explicitly designed to be assigned at data-construction time (the deterministic-country-package convention: randomness lives in the data package). Populace should assign them when building US microdata:

1. SNAP ABAWD discretionary exemptions — policyengine-us#8870 added is_snap_abawd_discretionary_exempt (person-level bool, default false, economy: false) with the statutory cap parameter gov.usda.snap.work_requirements.abawd.discretionary_exemption_rate (15% FY1998–2019, 12% FY2020–23, 8% FY2024+ of covered individuals, 7 U.S.C. 2015(o)(6)). Assignment should select among ABAWD-covered individuals up to the monthly-average share.
2. CHIP take-up — policyengine-us#8679 gates the household CHIP value on chip_enrolled = is_chip_eligible & takes_up_chip_if_eligible; takes_up_chip_if_eligible defaults true and the gov.hhs.chip.takeup_rate parameter (0.93) exists but is wired to nothing. Assigning take-up seeds in populace would activate the calibration and align CHIP aggregates with enrollment rather than eligibility.
3. Related earlier items in the same class remain open: SNAP ABAWD work-program participation hours (#8857's inputs), and the ACA take-up contract direction in policyengine-us#8693 (simulated take-up writes takes_up_aca_if_eligible directly).

Sourced from the July 2026 policyengine-us backlog sweep.

[daphnehanse11]

The SNAP half now has a PR: #353 seeds is_snap_abawd_discretionary_exempt with source-identity-keyed draws across potentially covered adults 18-64 at the 7 U.S.C. 2015(o)(6) cap (8% FY2024+), with the engine intersecting against modeled coverage — the same engine-intersects pattern #294 used for take-up. Full-cap usage is a documented assumption; USDA usage-report refinement stays open here. The Medicaid/CHIP half remains with #334/#337.