Read immutable closing-day source metadata

Verified lending staff/service authority; fresh staff step-up for writes. Capture occurs only on the actual closing bank date during the final fifteen minutes before cutoff, binds an immutable plan version, verifies accrual/recognition and prepares due facility bills, retains risk/billing evidence, and seals instrument mutations until cutoff. A source cannot be reconstructed on a later day. Next-day billing consumes already-generated minimum/due state without inventing delivery evidence. CECL execution may name close_source_id and compares dated ledger receivables to the exact retained source.