Add SOI state AGI taxable interest facts

[MaxGhenis]

Summary

• emit SOI Historic Table 2 state-by-AGI taxable interest return-count and amount facts from existing N00300/A00300 columns
• add explicit income_range: 500k_plus filters to the open-ended state AGI rows so consumers do not confuse them with all-income totals
• update source-package fixture counts for the expanded measure surface
• add a regression test for CA 200k-500k and 500k-plus taxable interest facts, geography, source columns, filters, and AGI constraints

Tests

• uv run python -m pytest tests/test_arch_source_package.py::test_national_soi_source_package_aliases_validate_fixture_counts tests/test_arch_source_package.py::test_soi_historic_table_2_state_agi_package_builds_taxable_interest_facts -q
• uv run ruff check tests/test_arch_source_package.py
• uv run ruff format --check tests/test_arch_source_package.py
• git diff --check

Companion Populace PR: PolicyEngine/populace#176