Cancel an open order by `orderId`. Returns the cancelled order payload after the status flip. Side effect: marks the order non-matchable and refunds locked balance per backend rules; effectively destructive on the live order. Idempotent — cancelling an already-cancelled order is a no-op success. Fails for fulfilled orders or unauthorized callers. Requires a signature session and `mcp-session-id`. Verify state with `tronsave_get_order` first; prefer `tronsave_update_order` when only price/receiver should change.
Connector