Add CMS ACA 2025 OEP source package

[MaxGhenis]

Summary

• adds the CMS ACA 2025 OEP state-level public-use-file source package
• emits 2025 state marketplace plan selections, APTC recipient counts, and average monthly APTC facts
• wires the source-package alias and adds focused count/value/lineage tests beside the existing CMS ACA OEP packages

Local validation

• uv run --python 3.13 ruff check arch/source_package.py tests/test_arch_source_package.py
• uv run --python 3.13 pytest -q tests/test_arch_source_package.py -k 'cms_aca_oep_state_level_2025 or cms_aca_oep_2025'
• uv run --python 3.13 arch validate-package cms-aca-oep-state-level-2025 --year 2025
• uv run --python 3.13 arch build-suite cms-aca-oep-state-level-2025 --year 2025 --out /tmp/arch-cms-aca-oep-state-level-2025 --replace

Build-suite output: 153 consumer facts, 54 source rows, 5,610 source cells, lineage coverage 1.0, 0 agent-acceptance errors.

Microplex note

This is source readiness for 2025 ACA marketplace controls. Current Microplex ACA PTC multiplier construction is still keyed to the 2022-to-2024 source pair; this package gives the next OEP target-year facts once Microplex chooses a 2025 ACA target recipe.