Propose posting, returning or writing off a clearing file exception

Verified staff on the card clearing desk's narrow scopes only: cards:clearing:read for reads, cards:clearing:write with a step-up within five minutes for writes; cards:write does not reach these routes and no service token or API key does. The file formats are bank-defined approximations of the proprietary Visa BASE II, Mastercard IPM and Discover clearing specifications (services/cards/clearing/README.md); a file from the card clearing simulator is simulated, not network traffic. Proposes how an open exception ends: post (the record to a named card of the same network, through the clearing or refund path), return (an issuer return instruction to the network; its later return credit or debit in a clearing file clears the suspense) or write_off (a debit item the bank absorbs to 5500, only once the file settlement carried it into suspense). A reason and 1 to 50 retained evidence references with lowercase SHA-256 are required. Nothing moves until a different reviewer approves the exact proposal. One pending proposal per exception; refused while a settlement of the exception's file awaits review or application. The same proposal by the same maker under the same key replays.