Bump PolicyEngine US for data builds

[MaxGhenis]

Summary

• require PolicyEngine US 1.691.10 for data builds
• resolve PolicyEngine US from exact upstream commit 4fd79e6608bc2dac3a7fde0be37191cb4870bd85 while PyPI publication is blocked
• add a changelog note for the dependency bump

Why

PolicyEngine US PR #8298 fixed vectorized calculations that affect SNAP disability eligibility, Medicaid medically needy categories, TANF non-cash asset tests, and capital-gains flags. The latest PyPI release remains 1.691.3; PE-US 1.691.10 built but failed to upload because the PyPI project hit the 10 GB storage limit. I filed PolicyEngine/policyengine-us#8316 for that release blocker.

On the current enhanced_cps_2024.h5, comparing PE-US 1.691.3 to upstream 1.691.10 for 2024 shows the old vectorization bug was material before any recalibration:

• is_usda_disabled weighted mean: 1.000 -> 0.126
• has_qdiv_or_ltcg weighted mean: 1.000 -> 0.182
• SNAP total: $109.4B -> $101.0B (-7.7%)
• SNAP eligible SPM units: 36.7M -> 34.0M (-7.3%)

That means the ECPS should be regenerated/recalibrated against the fixed model, not only rescored downstream.

Tests

• uv sync --extra calibration
• uv run pytest tests/unit/test_import.py tests/unit/test_enhanced_cps.py -q
• uv lock --check