feat(safety-sell): dcy-007 core 자율 안전 매도 — BAT-010 기반 + BAT-011 트리거

dcy-007(core 자율 안전 매도) 전체 delivery. BAT-010 기반 인프라가 미커밋
상태였고 BAT-011 트리거 레이어와 공유 파일에서 섞여 있어 한 커밋으로 묶음.

BAT-010 (REQ-034/035/036/041, release-candidate):
- WatchdogStore(application/watchdog.py) + snapshot RPC 워치독 갱신
- Slot stop_loss_price/take_profit_price 필드 + 004_add_price_thresholds.sql
- SlotService.sell() 자율 매도 내부 경로 + idempotency
- SafetySellConfig env 5종 파싱

BAT-011 (REQ-037/038/039/040/042, release-candidate):
- SafetySellService(application/safety_sell.py): forced_close 만기 / stop-loss·
  take-profit KIS polling / 장 마감 강제 청산 + trex-safety-sell 7번째 스레드
- BrokerPort.get_current_price + KIS inquire-price(TTTC8397R/VTTC8397R, stck_prpr)
  + paper stub
- SlotService.update_thresholds() + intent RPC update_thresholds 액션
  (부분 갱신/null 해제, 워치독 last_seen_at 리셋)
- baseline 3문서 정합(interface-contract/runtime-flows/project-structure)

거버넌스: REQ-034~042 Implemented 동기화, BAT-010/011 release-candidate,
dcy-007 discovery 포함.

검증: 신규 38 테스트 green, 단위 236 passed/23 skipped,
인프라 게이트(PG+RabbitMQ) 259 passed(마이그레이션 001~004 round-trip 포함),
ruff clean.

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

trex_core/adapters/broker/paper.py

@@ -8,6 +8,7 @@ execution code path that production (KIS) takes.
 from __future__ import annotations
 
 import threading
+from decimal import Decimal
 from typing import Optional
 
 from trex_core.application.broker_port import (
@@ -52,6 +53,8 @@ class PaperBroker:
         self._orders: dict[str, _Order] = {}
         self._seq = 0
         self._lock = threading.Lock()
+        # REQ-038: programmable current price for safety-sell scenario tests.
+        self._prices: dict[str, Decimal] = {}
 
     def name(self) -> str:
         return "paper"
@@ -111,3 +114,14 @@ class PaperBroker:
                 balances[o.symbol] = balances.get(o.symbol, 0) + sign * int(o.filled)
         return [BalanceItem(symbol=sym, hldg_qty=qty)
                 for sym, qty in balances.items() if qty != 0]
+
+    # --- REQ-038: programmable current price (safety-sell scenario double) ---
+    def set_current_price(self, symbol: str, price: Decimal) -> None:
+        """Program the current price returned by get_current_price(symbol)."""
+        with self._lock:
+            self._prices[symbol] = Decimal(str(price))
+
+    def get_current_price(self, symbol: str) -> Optional[Decimal]:
+        """Return the programmed current price for symbol, or None if unset."""
+        with self._lock:
+            return self._prices.get(symbol)