Reserve available master cash and issue exact existing-debt repayment

Fresh verified staff with ledger:repo:write is required. Reserves actual available bank master cash when the supported debt is due and issues a separate immutable repayment command binding actual funding, original principal/interest and hold. The initial borrowing cannot authorize an unreserved future debit. Existing proven debt can be reduced despite collateral monitoring exceptions; unsupported changed contract/default amounts refuse. Every route requires verified non-API-key authority even locally; customer actors are refused. JSON evidence is one strict object bounded at 5 MiB. Complete responses are bounded at 16 MiB and fail explicitly without truncation.