List contracts with funding rollups (attention-first)

DARK — 404s unless ar_ap_items_enabled. Each contract carries a derived funding rollup {contractedCents, invoicedToDateCents, remainingCents, pctInvoiced, isFullyInvoiced} computed from its non-void AR items (linkage sourceMetadata.contractId); invariant invoicedToDate + remaining = contracted. Sorted attention-first (remaining > 0 or status overdue), then by contracted value. The envelope also carries totalContractedCents and activeContractCount (active = not cancelled/completed), plus currency and minorUnitExponent. Funding rollups carry the same non-null currency authority. Mixed, invalid, missing, or non-two-decimal source currencies fail with MONETARY_AGGREGATE_CURRENCY_UNAVAILABLE (422).