Tennessee children's Medicaid income limits stored as flat 216% FPL for all age bands

`gov/hhs/medicaid/eligibility/categories/{infant,young_child,older_child}/income_limit.yaml` store TN = 2.16 (flat) since 2018-01-01 for all three child age bands.

TennCare's actual limits are age-banded: infants under 1 at 195% FPL, ages 1–5 at 142%, ages 6–18 at 133% — effective 200% / 147% / 138% with the 5-point MAGI disregard (TennCare Eligibility Reference Guide: https://www.tn.gov/content/dam/tn/tenncare/documents/eligibilityrefguide.pdf). A flat 216% for all bands matches no current source (CMS eligibility-levels table, KFF Jan-2026 state indicators, TennCare's own guide).

Found while cross-validating PolicyEngine against the Axiom rules corpus (TheAxiomFoundation/axiom-oracles, suite `medicaid-thresholds-states`), where the three TN child rows are dispositioned as an upstream gap.

Start with gov/hhs/medicaid/eligibility/categories/{infant,young_child,older_child}/income_limit.yaml and compare the Tennessee rows with TennCare's Eligibility Reference Guide and the cited CMS and KFF sources. Update the three age bands so their limits match the authoritative current values, then verify the Medicaid threshold data against the medicaid-thresholds-states corpus; done means no flat 2.16 value remains for these Tennessee rows.

Written by the indexing model from the issue text.