Fix PriceResult slots serialization that broke open-group response.

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

backend/app/sim/matcher.py

@@ -213,8 +213,8 @@ class Matcher:
             detail="opened",
             data={
                 "group_id": group_id,
-                "perp": pf.__dict__,
-                "option": of.__dict__,
+                "perp": pf.to_dict(),
+                "option": of.to_dict(),
                 "initial_premium": initial_premium,
                 "fees": pf.fee + of.fee,
             },

backend/app/sim/pricing.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from dataclasses import dataclass
+from dataclasses import asdict, dataclass
 
 
 @dataclass(slots=True)
@@ -13,6 +13,9 @@ class PriceResult:
     slip: float
     notional: float
 
+    def to_dict(self) -> dict[str, float]:
+        return asdict(self)
+
 
 def perp_fill(
     *,