Add SNAP work requirement state coverage tests and limitation diagnostics

[daphnehanse11]

Fixes #8825

Summary

Adds a lightweight, inspectable coverage artifact for SNAP OBBBA work-requirement state coverage, per #8825 (child of tracker #8820). No formula or parameter logic is changed — this PR only documents and tests the current state of the model.

• policyengine_us/parameters/gov/usda/snap/work_requirements/README.md: rule-by-rule and state-by-state coverage tables covering general work registration (7 CFR 273.7), the ABAWD time limit (7 CFR 273.24), and the HR1/OBBBA changes (P.L. 119-21, effective 2025-07-04). It records:
  • Modeled rules: 30-hour general and 20-hour ABAWD thresholds, HR1 age and dependent-child threshold changes, removal of pre-HR1 homeless/veteran exemptions, pregnancy exemption, and California's delayed HR1 implementation (2026-06-01 per ACL 25-93).
  • Partially modeled: the Indian/Urban Indian/California Indian ABAWD exemption is consumed by the formula but is an input variable with no formula (defaults to false unless supplied).
  • Pending gaps with issue links: HI/AK delayed adoption and the unconsumed exempt_states parameter (SNAP ABAWD: model HI/AK delayed HR1 implementation and consume exempt-state parameter #8821), Alaska borough-level waivers (SNAP ABAWD: model Alaska borough-level waiver geography #8822), qualifying work-program hours (SNAP ABAWD: support qualifying work-program participation or hours #8823), and omitted non-age work-registration exemptions (SNAP work registration: add omitted non-age exemption hooks #8824).
  • Data-dependent input limitations (hours worked, pregnancy, Indian status, etc.), with a pointer to SNAP OBBBA work requirements: restore data inputs needed for household exposure analysis populace#248.
  • A note that the artifact must be updated as child issues SNAP ABAWD: model HI/AK delayed HR1 implementation and consume exempt-state parameter #8821–SNAP work registration: add omitted non-age exemption hooks #8824 land.
• policyengine_us/tests/policy/baseline/gov/usda/snap/eligibility/work_requirements/state_coverage.yaml: coverage tests of is_snap_abawd_hr1_in_effect for default-rule states (TX, NY) before and after the federal 2025-07-04 effective date, and California before and at its 2026-06-01 adoption date. HI/AK cases are intentionally not asserted (current behavior is a known gap being fixed in the SNAP ABAWD: model HI/AK delayed HR1 implementation and consume exempt-state parameter #8821 PR); they are documented in the README instead.

Test output

uv run policyengine-core test policyengine_us/tests/policy/baseline/gov/usda/snap/eligibility/work_requirements -c policyengine_us
======================== 66 passed, 1 warning in 8.19s =========================

🤖 Generated with Claude Code