Map Arch SOI alimony targets

[MaxGhenis]

Summary

• map Arch SOI Table 1.4 alimony received and paid facts into Microplex targets
• include alimony paid as a source-backed PolicyEngine target now that Arch has a primary SOI source
• add regression coverage for Arch consumer-fact mapping and source-backed profile counts

Validation

• uv run ruff check src/microplex_us/targets/arch.py src/microplex_us/policyengine/target_profiles.py tests/targets/test_arch.py tests/targets/test_arch_facts.py tests/policyengine/test_target_profiles.py
• uv run --extra dev --extra policyengine python -m pytest tests/policyengine/test_target_profiles.py tests/targets/test_arch.py::test_arch_provider_matches_current_profile_aliases tests/targets/test_arch_facts.py::test_arch_consumer_fact_jsonl_provider_maps_soi_alimony_concepts -q
• refreshed pe_native_broad_source_backed coverage with updated Arch sources: 167/167 covered, 0 uncovered

Depends on merged PolicyEngine/arch-data#33.