feat: propagate intent venue through execution

trex_core/domain/slot/models.py

@@ -56,6 +56,9 @@ class Slot:
     # holding episode. Used by the strategy-state CAS to reject writes computed
     # against a prior occupancy of a reused slot (point-ABA guard, dcy-028 R-1).
     occupancy_seq: int = 0
+    # Order venue carried from the admitted intent through dispatch/cancel.
+    # It is reset to KRX when the permanent asset slot returns to INACTIVE.
+    venue: str = "KRX"
 
 
 # Canonical column contract for `Slot` (dcy-001 OQ-2 / FR-5).
@@ -84,6 +87,7 @@ EXPECTED_SLOT_FIELDS: frozenset[str] = frozenset({
     "timeout_sec",        # dcy-022 / REQ-068 (BAT-032)
     "slippage_pct",       # dcy-022 / REQ-068 (BAT-032)
     "occupancy_seq",      # dcy-028 / REQ-081 (BAT-042)
+    "venue",
 })