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/vest-class.ts

@@ -47,13 +47,13 @@ import {
 import { getCachedFirm } from './firm-catalog';
 import { firmInstruments } from './instruments';
 import type { PlatformClient, PlatformAccount, PlatformContract, ClientHealth, PickContext, OrderIntent } from './platform-client';
-import { OrderNotPlacedError, NothingToCloseError, isOrderNotPlaced, errorMessage } from './platform-client';
+import { OrderNotPlacedError, isOrderNotPlaced, errorMessage, orderEffect } from './platform-client';
 import { encodeContractName, decodeContractName, roundToStep, scoreCandidate } from './dxtrade-helpers';
 import { vestSessionFor, dropVestSession, listVestSessions, refuseVestSession } from './vest-session';
 import {
     vestAccountId, vestAccountName, vestDayOf, lastVestResetMs, nextVestResetMs, parseCapitalAccount, parsePosition, parseOpenOrder,
     parseTxn, bookTxns, awaitingLegs, unrealizedPnl, hourlyVolatility, marketOpen, num, toMs, formatDecimal, resetSafeStop,
-    parseHistoryPosition, jwtClaimStrings, accountScopedToken, vestOrderEffect, VEST_STATUS_ACTIVE, VEST_TXN, VEST_STOP_SLIPPAGE_FRACTION,
+    parseHistoryPosition, jwtClaimStrings, accountScopedToken, VEST_STATUS_ACTIVE, VEST_TXN, VEST_STOP_SLIPPAGE_FRACTION,
 } from './vest-helpers';
 import type { VestCapitalAccount, VestPosition, VestOpenOrder, VestTxn, VestTrade } from './vest-helpers';
 
@@ -1606,7 +1606,7 @@ export class VestClient implements PlatformClient {
     /**
      * Place an order and wait for its fill: an open when the account is flat,
      * a close (or reduce) of the position when it holds the opposite side —
-     * only the one `intent` names, when given (vestOrderEffect). Adding to a
+     * only the one `intent` names, when given (orderEffect). Adding to a
      * position is refused, and so is an open against another account's
      * opposite position in the same symbol (no hedging). Resolves with the
      * fill `price`.
@@ -1645,9 +1645,10 @@ export class VestClient implements PlatformClient {
         } catch (err) {
             throw new OrderNotPlacedError(`Vest position check failed — order not sent: ${errorMessage(err)}`);
         }
-        const existing = positions.find((p) => p.symbol === symbol);
-        const route = vestOrderEffect({ symbol, held: existing?.side ?? null, side, intent });
-        if ('refused' in route) throw route.nothingToClose ? new NothingToCloseError(route.refused) : new OrderNotPlacedError(route.refused);
+        const held = positions.find((p) => p.symbol === symbol);
+        const recorded = this.positionsDetail.get(accountId)?.find((p) => p.symbol === symbol)?.side ?? null;
+        // orderEffect picks open or close; `existing` is the position a close closes.
+        const existing = orderEffect({ symbol, held: held?.side ?? null, recorded, side, intent }) === 'close' ? held : undefined;
 
         const units = roundToStep(contracts * step, step);
         const qty = (n: number) => formatDecimal(n, spec.sizeDecimals);