Long-term CPS projections (2026–2100) have no populace replacement — decide rebuild / inherit / retire before #204 closes

The populace#204 replacement audit (table on that issue) found one artifact family with no code-level populace replacement, not even pending: the long-term CPS projections (long_term/*, 75 single-year datasets 2026–2100) shipped by the archived policyengine-us-data. Two independent zero-match searches across populace confirm nothing addresses it — this is distinct from target-side aging (ledger cbo_growth_factor_aging), which ages the calibration surface, not the microdata records.

Decision needed before #204 can close: (a) rebuild long-term projections as a populace product (the populace-dynamics trajectory work is the natural eventual home — cf. populace-dynamics#45's design reservations), (b) explicit temporary inheritance from the archived artifacts with a documented sunset, or (c) declare out of scope with consumer migration notes. Consumers and evidence are in the #204 table.

Start with the consumers and evidence in issue #204, then inspect the long_term/* datasets covering 2026–2100 and the populace-dynamics#45 design reservations. Determine whether these artifacts have a supported replacement path, inheritance plan, or retirement requirements; done means one option is documented with migration implications before #204 closes.