DXtrade sizing: volatility only (12h default hold); fees and every-day only for DXtrade

The symbol map's fixed notional per contract is gone: every DXtrade leg is
sized from the instrument's recent volatility for the firm's target hold
(blank = 12 h), and a candidate without a volatility isn't picked. Percent
commission and every-day trading are ignored on non-DXtrade firms, which keep
measured per-contract fees and the CME calendar.

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

lib/dxtrade-class.ts

@@ -31,7 +31,7 @@
  */
 
 import axios from 'axios';
-import { currentTradeDateCT, FIRM_RESET_UTC_HOUR } from './trading-logic';
+import { currentTradeDateCT, FIRM_RESET_UTC_HOUR, DEFAULT_TARGET_HOLD_HOURS } from './trading-logic';
 import {
     saveDailyPnL, loadDailyPnL, loadAccountMeta, saveAccountMeta, loadFundTransactions, saveFundTransactions,
     saveEndedCycleStart,
@@ -1102,8 +1102,8 @@ export class DXTradeClient implements PlatformClient {
 
     /**
      * The contract a CME root trades as on this firm right now: the cheapest
-     * tradable candidate from the symbol map, per unit of volatility when the
-     * firm sizes by target hold (see scoreCandidate). Sticky while an account
+     * tradable candidate from the symbol map, per unit of volatility (see
+     * scoreCandidate). Sticky while an account
      * holds one of the candidates, cached briefly so a batch's lookups agree.
      */
     public async findFrontMonthContract(root: string): Promise<PlatformContract | null> {
@@ -1134,13 +1134,13 @@ export class DXTradeClient implements PlatformClient {
         const ref = this.referenceAccount();
         if (!ref) return null;
         const firm = getCachedFirm(this.cfg.firmId);
-        const targetHold = firm?.targetHoldHours ?? 0;
+        const targetHold = firm?.targetHoldHours || DEFAULT_TARGET_HOLD_HOURS;
         const symbols = [...new Set(candidates.map((c) => c.symbol))];
         const [insts, dets, quotes, vols] = await Promise.all([
             this.instruments(symbols),
             this.accountInstruments(ref.code, symbols),
             this.quotes(ref.code, symbols),
-            targetHold > 0 ? this.volatility(ref.code, symbols) : Promise.resolve(new Map<string, { vol: number | null; candles: number }>()),
+            this.volatility(ref.code, symbols),
         ]);
 
         const now = new Date();
@@ -1178,7 +1178,6 @@ export class DXTradeClient implements PlatformClient {
                     quoteAgeMs: quote && Number.isFinite(quote.time) ? Date.now() - quote.time : null,
                     inHours: inTradingHours(inst.tradingHours, now),
                     candles: vol?.candles ?? 0,
-                    needVolatility: targetHold > 0,
                     minContractsOk: maxContracts === undefined || maxContracts >= minContracts,
                     currency: typeof inst.currency === 'string' ? inst.currency : undefined,
                     accountCurrency: ref.currency,
@@ -1204,7 +1203,6 @@ export class DXTradeClient implements PlatformClient {
                     pointValue: step * multiplier,
                     commissionPct: pct,
                     stepNotional,
-                    fixedNotional: cand.notionalPerContract,
                     volatilityPerHour: vol?.vol ?? undefined,
                     spreadFraction: spread,
                     maxContracts,