DXtrade: count closed-trade P&L, week-long volatility, broker leverage caps, swap in the take-profit

- Transfers: a close books its SETTLEMENT and COMMISSION under one
  transaction code, and keying by the code alone let the commission
  overwrite the P&L. Keys now carry the type, so the day-start balance,
  daily-loss room, realized P&L, daily history and books check all see
  closed-trade profit and loss.
- Volatility from a week of hourly closes (was 48 h), still measured once
  per trade date, so one quiet weekend can't triple a hold estimate.
- Each symbol's margin rate from the account's instrument details caps
  the position at available funds / rate (Tradeify: 5:1 crypto, 2:1
  stocks); the account type's max notional stays as an optional ceiling.
- Firms with overnight financing add the swap a winning leg is expected
  to pay (the winners' mean hold, (A²+2AB)/3σ²) to its take-profit, and
  the sizing and hold estimate count it.

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

README.md

@@ -116,14 +116,20 @@ per-contract fees and the CME calendar.
 - **Symbol map** — which DXtrade symbols each CME root may trade as. A `*` row
   covers every root (drain and extra-day legs trade `MNQ`, so map it or use
   `*`). When a root lists several, the cheapest tradable one right now wins:
-  spread plus both commissions, divided by its recent hourly volatility.
-- **Target hold hours** — each leg's notional is sized from the instrument's
-  recent volatility so its expected hold is about this long (blank = 12 h),
-  and **financing %/day** if the firm charges swap.
+  spread plus both commissions, divided by its volatility (hourly closes over
+  the past week, measured once a day).
+- **Target hold hours** — each leg's notional is sized from that volatility so
+  its expected hold is about this long (blank = 12 h). The position never
+  exceeds what the account's available funds can margin at the broker's
+  rate for the symbol (Tradeify: 5:1 crypto, 2:1 stocks), so a quiet market or
+  a big leg can hold longer than the target.
+- **Financing %/day** if the firm charges swap (Tradeify 1-Step: `0.033`).
+  Each take-profit then also carries the swap a winning leg is expected to pay
+  before it fills, so a win still clears the full leg.
 
 Per account type: **Daily loss limit** (Tradeify: 3% of size — every leg then
 carries a stop that keeps the firm's day inside it, less a 10% reserve and
-fees) and **Max notional**.
+fees) and **Max notional**, an optional ceiling on top of the broker's margin.
 
 Before the scheduler trades a DXtrade firm, run the smoke test against a real
 login (with this instance's client for the firm disconnected):