NZ source packages, wave 2: take-up and validation surface

[juaristi22]

Lane: ledger-source-ingestor — judges ledger-source-fidelity + ledger-boundary
Depends on: #176 (conventions established; the M1d shape proven before its HUD duplicate lands)

Context

The populace-nz product is a dollar take-up gap: full-entitlement modelled dollars vs dollars actually paid. Wave 1 carries the calibration margins; this wave carries the comparison and validation surface — the facts the take-up computation and the gates read but calibration must not bind. Several rows are provenance_class: model_output or assertion: source_projection; the populace-side assertion-policy story (allow_source_projection, diagnostic-only families) must be settled per package before it lands.

Candidate inventory

Package	Artifact	Why wave 2
treasury/an24_01_fiscal_totals	fiscal_totals.csv from the AN 24/01 companion repo (CC0)	Program-level admin dollar totals (TY2018/19) as a validation cross-check — stale vintage, not a calibration margin
treasury/distribution_explorer_hes24_befu25	DistributionExplorer DE_HES24_BEFU25_TY{25..29}_SQ.csv (MIT)	The full-entitlement denominator, provenance_class: model_output — never calibrated to; diagnostic band only (NBB macro-realism precedent)
hud/housing_dashboard_as_2026	Housing Dashboard data-download xlsx, AS tab	TLA-grain AS counts duplicating M1d — lands after the M1d shape is proven; 14 MB monthly workbook needs sheets: discipline
msd/hardship_assistance_march_2026	Fact-sheet supplementary xlsx (grants and dollars)	Quarterly hardship $ — small program, not in the 16 margins
ird/kiwisaver_statistics_2026	IRD KiwiSaver datasets xlsx	Members/contributions — relevant when KiwiSaver rules enter the composed surface
msd/befu_2025_benefit_forecasts	BEFU 2025 recipient forecasts	Forward periods, assertion: source_projection — needed only when populace targets years beyond observed vintages

Acceptance

Same per-package provenance/guard/acceptance bar as #176; every model_output and source_projection row's intended populace-side treatment (diagnostic family, assertion policy) named in the PR description; no computed values.

Out of scope

Calibrating to any of these facts (populace-side gate design); local geography (#178).

Sizing

~6 packages ≈ 2–3 PRs (treasury batch, MSD/HUD batch, IRD).