DXtrade: an entry never closes a hand trade, and a flatten never opens one

DXtrade dropped the intent the engine now passes, so on the live
Tradeify247 accounts an entry could still close a hand position as the
"entry" and the leg's flatten then OPEN a position with no exits. The
open/close decision moves out of vest-helpers into platform-client's
orderEffect, which both clients now follow to pick OPEN or CLOSE.

A flatten's flat read is "nothing to flatten" only when the client's own
record agrees. One empty read just after a fill the client saw may be the
gateway lagging, so it stays a plain refusal and keeps the FLATTEN FAILED
alarm. A check now fails if an engine order drops its intent or a client
stops going by orderEffect.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/auto-trade.ts

@@ -260,9 +260,10 @@ function unrecordLeg(accountId: number, tradeDate: string, legAmount: number): v
  * (OrderNotPlacedError). Anything ambiguous, like an ack or fill timeout,
  * keeps the leg: the order may well have filled, and a leg counted that never
  * happened only costs a leg, while one forgotten that did can trade the
- * account twice. Open-only: where the platform checks (Vest), an account that
- * already holds the symbol — a hand trade the synced positions don't show
- * yet — is refused rather than having that position closed as the "entry".
+ * account twice. Open-only: where the platform checks (Vest, DXtrade), an
+ * account that already holds the symbol — a hand trade the synced positions
+ * don't show yet — is refused rather than having that position closed as the
+ * "entry".
  */
 async function sendEntry(
     tag: string,
@@ -1304,8 +1305,9 @@ const round2 = (n: number) => Math.round(n * 100) / 100;
  * report the leg as failed. A flatten that fails too is the worst case: a
  * position with no stop, so it is shouted about. Close-only: on an account
  * that turned out flat it must not open a fresh position with no exits, and
- * where the platform checks (Vest) that flat account has nothing riding — the
- * leg still fails, but without the alarm.
+ * where the platform checks (Vest, DXtrade) and its own record agrees, that
+ * flat account has nothing riding — the leg still fails, but without the
+ * alarm. A flat read the record contradicts still gets the alarm.
  */
 async function flattenAndFail(
     tag: string,