Add export lineage gate

[MaxGhenis]

Summary

• add a generated eCPS export lineage manifest that maps each required export to static source/code evidence
• add an mp300k export_lineage gate so eCPS-populated required exports cannot pass with only PE-US defaults
• populate weekly_hours_worked_before_lsr from CPS hours_worked/hours_worked_last_week instead of falling back to a constant default

Notes

• This deliberately does not require or export slcsp; slcsp should remain computed by PE-US from geography/age/family inputs.
• Against latest local enhanced_cps_2024.h5, the manifest now reports one remaining eCPS-populated default-only export: selected_marketplace_plan_benchmark_ratio. That is the persisted selected-plan ratio input, not slcsp.

Tests

• uv run --python 3.13 --extra dev ruff check src/microplex_us/pipelines/mp300k_artifact_gates.py src/microplex_us/pipelines/export_lineage_manifest.py src/microplex_us/pipelines/us.py src/microplex_us/policyengine/us.py tests/pipelines/test_mp300k_artifact_gates.py tests/pipelines/test_export_lineage_manifest.py tests/pipelines/test_us.py tests/policyengine/test_us.py
• uv run --python 3.13 --extra dev ruff format --check src/microplex_us/pipelines/mp300k_artifact_gates.py src/microplex_us/pipelines/export_lineage_manifest.py src/microplex_us/pipelines/us.py src/microplex_us/policyengine/us.py tests/pipelines/test_mp300k_artifact_gates.py tests/pipelines/test_export_lineage_manifest.py tests/pipelines/test_us.py tests/policyengine/test_us.py
• uv run --python 3.13 --extra dev python -m pytest tests/pipelines/test_export_lineage_manifest.py tests/pipelines/test_mp300k_artifact_gates.py -k 'export_lineage or passes_with_all_evidence'
• uv run --python 3.13 --extra dev python -m pytest tests/pipelines/test_mp300k_artifact_gates.py
• uv run --python 3.13 --extra dev python -m pytest tests/pipelines/test_us.py -k 'augment_policyengine_person_inputs_materializes_export_support_aliases'
• uv run --python 3.13 --extra dev python -m pytest tests/policyengine/test_us.py -k 'time_period_arrays_derive_ecps_persisted_computed_inputs'