malkhut(wire): BingX adapter uses standardized OrderType mapping

adapter.py now uses normalize_to_exchange(action.order_type, 'bingx')
to translate normalized order types to BingX-native strings.
Falls back to LIMIT/MARKET/POST_ONLY for backward compatibility.

This is the critical integration point: standardized order types flow
from FulfilmentAction → CWM → VenueAdapter → exchange API.

MALKHUT/malkhut/venue/bingx/adapter.py

@@ -177,12 +177,16 @@ class BingXVenueAdapter:
         self._order_seq += 1
         client_id = f"m_{state.ts_ns}_{self._order_seq}"
 
-        # Determine order type
-        order_type = "LIMIT"
-        if action.kind.value == "CROSS_SPREAD":
+        # Determine order type — use standardized OrderType, map to BingX-native
+        from malkhut.training.order_types import normalize_to_exchange
+        if action.order_type is not None:
+            order_type = normalize_to_exchange(action.order_type.value, "bingx") or "LIMIT"
+        elif action.kind.value == "CROSS_SPREAD":
             order_type = "MARKET"
         elif action.post_only:
             order_type = "POST_ONLY"
+        else:
+            order_type = "LIMIT"
 
         # Build order
         order = {