Report bank settlement of observed ERP payments

After posting, the native ERP shell reports whether each observed payment has been matched to a bank statement. Commerce Gate records drift when a payment stays unsettled past the company's window (payment_unsettled, cleared once it settles or is voided) or settles at a different amount than it posted (payment_settled_mismatch, which a person reviews). Business Central uses the same current workspace key and full native_context checks as payment validation. Each item must match a saved posted OBSERVE anchor, including its exact entry_id, payment, vendor, amount and currency. event_id and sequence are immutable per-payment event identity; exact retries do not count twice, stale sequences do not change drift, and settled or voided payments cannot reopen. Reusing an event identity with different facts returns 409; a batch commits atomically. The envelope timestamp is excluded from event identity and is not an independently verified occurrence time. F&SCM retains its existing credential/tenant behavior. Nothing is sent to Decionis, no account data crosses the boundary, and nothing moves money. A 503 means the report was not recorded and the ERP should retry. This is an unreleased source candidate.