fix(trend): correct DCA triggers and partial-position PnL across exchanges

Co-authored-by: Cursor <cursoragent@cursor.com>

strategy_trend_lib.py

@@ -24,6 +24,40 @@ def calc_risk_fraction(direction: str, entry_price: float, stop_loss: float) ->
         return None
 
 
+def trend_effective_margin_capital(plan: dict) -> float:
+    """按已开仓张数占计划总张数比例折算保证金（首仓/部分补仓时的盈亏估算）。"""
+    try:
+        plan_margin = float(plan.get("plan_margin_capital") or 0)
+        target = float(plan.get("target_order_amount") or 0)
+        open_amt = float(plan.get("order_amount_open") or 0)
+    except (TypeError, ValueError):
+        return float((plan or {}).get("plan_margin_capital") or 0)
+    if plan_margin <= 0:
+        return 0.0
+    if target > 0 and open_amt > 0:
+        return round(plan_margin * min(1.0, open_amt / target), 8)
+    try:
+        first = float(plan.get("first_order_amount") or 0)
+    except (TypeError, ValueError):
+        first = 0.0
+    if target > 0 and first > 0:
+        return round(plan_margin * min(1.0, first / target), 8)
+    return plan_margin
+
+
+def trend_dca_level_reached(direction: str, mark_price: float, level: float) -> bool:
+    """做空：价升触达/越过档位即应补仓；做多：价跌触达/越过档位。"""
+    d = (direction or "long").strip().lower()
+    try:
+        pf = float(mark_price)
+        lv = float(level)
+    except (TypeError, ValueError):
+        return False
+    if d == "long":
+        return pf <= lv
+    return pf >= lv
+
+
 def validate_trend_bounds(direction: str, stop_loss: float, add_upper: float) -> Optional[str]:
     direction = (direction or "long").strip().lower()
     if direction == "long":