feat: resolve and persist actual order venue

trex_core/domain/slot/service.py

@@ -215,10 +215,15 @@ class SlotService:
             new_limit_price = limit_price if limit_price is not None else slot.limit_price
             new_timeout_sec = timeout_sec if timeout_sec is not None else slot.timeout_sec
             new_slippage_pct = slippage_pct if slippage_pct is not None else slot.slippage_pct
+            new_venue = venue if venue is not None else slot.venue
         else:  # HOLDING / ERROR — pending order policy no longer applies.
             new_limit_price = None
             new_timeout_sec = None
             new_slippage_pct = None
+            # A completed order's venue must not leak into a later autonomous
+            # sell. The next order starts session-aware unless its intent
+            # explicitly chooses KRX/NXT/SOR.
+            new_venue = "AUTO" if to_state is SlotState.HOLDING else slot.venue
 
         # occupancy_seq (dcy-028/REQ-081): bump when a slot begins a new
         # occupancy (inactive→pending_buy). Stable across the rest of the
@@ -271,7 +276,7 @@ class SlotService:
             timeout_sec=new_timeout_sec,
             slippage_pct=new_slippage_pct,
             occupancy_seq=new_occupancy_seq,
-            venue=venue if venue is not None else slot.venue,
+            venue=new_venue,
             updated_at=datetime.now(tz=timezone.utc),
         )