feat(slot): BAT-027 M2/M3 — 상태머신 inactive 재정의 + 인스턴스 스코프 advisory lock (dcy-020/REQ-057)

안 B 점진의 2/3단계. runtime 무변경(idle/closed 별칭 흡수)으로 cascade 통제.

- state.py: SlotState.INACTIVE 추가 + idle/closed 별칭 normalize_state(); 전이 집합
  inactive 기준 재정의(inactive↔pending_buy↔holding↔pending_sell), closed→idle 제거;
  is_allowed_transition 양쪽 정규화; slot_advisory_lock_id(instance_key) 헬퍼
- service.py: SlotService(instance_key) + advisory lock 인스턴스 스코프(self._lock_id)
- __init__: normalize_state/slot_advisory_lock_id export; daemon: instance_key 전달
- 테스트 갱신: test_state(전이/멤버7/락/size12), test_service(closed→idle 제거→reallocation),
  test_slot_entry_count, test_postgresql_repository(closed→idle 거부+reallocation)

검증: 단위 375 passed / 35 skipped, PG-gated(trex_core_test) 8 passed
(마이그레이션 009 드리프트 + lifecycle/reallocation), ruff clean.

REQ-056/057 은 토대만 충족 → Approved 유지(entry_count/trading_date drop·literal
inactive 전면 전환은 BAT-δ; confirm-req-implemented 는 dcy-020 후속 배치 완료 후).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

trex_core/domain/slot/service.py

@@ -23,7 +23,11 @@ from trex_core.domain.slot.errors import (
 )
 from trex_core.domain.slot.models import Slot, SlotCapacity, SlotTransitionRecord
 from trex_core.domain.slot.repository import SlotRepository
-from trex_core.domain.slot.state import SLOT_ADVISORY_LOCK_ID, SlotState, is_allowed_transition
+from trex_core.domain.slot.state import (
+    SlotState,
+    is_allowed_transition,
+    slot_advisory_lock_id,
+)
 
 # Sentinel distinguishing "field omitted (keep current)" from "field set to
 # None (clear threshold)" in update_thresholds (REQ-040 AC-4 vs AC-5).
@@ -33,8 +37,12 @@ _UNSET: Any = object()
 class SlotService:
     """Slot lifecycle service. Race-free transitions via advisory lock + transaction."""
 
-    def __init__(self, repository: SlotRepository) -> None:
+    def __init__(self, repository: SlotRepository, instance_key: str = "default") -> None:
         self._repo = repository
+        # dcy-020/REQ-057: advisory lock is scoped per instance so a shared DB
+        # does not serialize transitions across instances (NFR-1).
+        self._instance_key = instance_key
+        self._lock_id = slot_advisory_lock_id(instance_key)
 
     # ------------------------------------------------------------
     # preallocate_daily_slots
@@ -49,7 +57,7 @@ class SlotService:
         """
         if count <= 0:
             raise ValueError(f"slot count must be > 0, got {count}")
-        with self._repo.transactional_advisory_lock(SLOT_ADVISORY_LOCK_ID):
+        with self._repo.transactional_advisory_lock(self._lock_id):
             return self._repo.pre_allocate_slots(trading_date, count)
 
     # ------------------------------------------------------------
@@ -96,7 +104,7 @@ class SlotService:
                 f"transition not allowed: {from_state.value} -> {to_state.value}"
             )
 
-        with self._repo.transactional_advisory_lock(SLOT_ADVISORY_LOCK_ID):
+        with self._repo.transactional_advisory_lock(self._lock_id):
             slot = self._repo.fetch_slot(slot_id)
             if slot is None:
                 raise SlotNotFoundError(f"slot not found: {slot_id}")
@@ -323,7 +331,7 @@ class SlotService:
         the holding state (AC-6). Raises SlotNotFoundError for unknown slots.
         The caller (RPC handler) resets the watchdog last_seen_at (AC-3).
         """
-        with self._repo.transactional_advisory_lock(SLOT_ADVISORY_LOCK_ID):
+        with self._repo.transactional_advisory_lock(self._lock_id):
             slot = self._repo.fetch_slot(slot_id)
             if slot is None:
                 raise SlotNotFoundError(f"slot not found: {slot_id}")