Tighten source-backed target profile

[MaxGhenis]

Summary

• exclude SALT raw/count cells that current Arch sources cannot support exactly
• exclude state AGI person-count cells because current SOI state AGI sources publish returns/amounts, not people
• keep national itemizer SALT amount in the source-backed profile because it is now composed from exact Table 2.1 components

Validation

• uv run ruff check src/microplex_us/policyengine/target_profiles.py tests/policyengine/test_target_profiles.py
• uv run --extra dev --extra policyengine python -m pytest tests/policyengine/test_target_profiles.py -q
• refreshed source-backed Arch coverage: 165/166, with only national alimony_income uncovered

Coverage artifact: /Users/maxghenis/CosilicoAI/microplex-us/artifacts/arch_source_backed_profile_exclusions_20260528/pe_native_broad_source_backed_2024_coverage_after_exclusions.json