Deliver BAT-004: broker execution + KIS adapter + durable handoff

Implement REQ-011~015 (dcy-003): the order-execution layer on top of the
BAT-002 slot-core daemon, connecting intents to real orders.
- application: BrokerPort (submit/poll_fill/cancel) + ExecutionService
  (claim -> submit -> poll -> transition -> rollback -> reconcile)
- adapters/broker: PaperBroker (deterministic async double) and KISBroker
  (KIS Open API: token, order-cash, inquire-daily-ccld, cancel; VTS sandbox
  tr_ids; live account gated behind allow_live)
- persistence: option-A execution queue (find_pending_for_dispatch FOR
  UPDATE SKIP LOCKED, mark_dispatched idempotency guard, clear_dispatch)
- runtime: background execution loop in the daemon lifespan + startup
  reconcile; config selects paper|kis

Verification (real KIS VTS 모의투자 + PostgreSQL): 92 passed, ruff clean,
domain import sweep shows zero broker/web/db deps, buy->holding /
sell->closed / reject->idle, idempotent dispatch (exactly one order),
reconcile after crash creates no duplicate order, KIS sandbox token+submit
round-trip, and a daemon E2E through the background loop. Align the four
baseline docs. BAT-004 -> release-candidate; REQ-011~015 -> Implemented.

KIS live-account go-live, partial-fill accrual, option-B outbox, connection
pooling, and the safety floor remain deferred to follow-up Discoveries.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/runtime-flows.md

@@ -45,6 +45,16 @@
 1. 전략 데몬이 holding 슬롯을 `GET /v1/slots?status=holding` 로 조회 후 sell intent POST.
 2. dedup 게이트 → 검증(slot 이 holding 인가) → `transit_slot(holding→pending_sell)` → finalize → 동기 응답.
 
+## Flow: `주문 집행 루프` (백그라운드, BAT-004)
+
+데몬 lifecycle 에서 시작되는 단일 백그라운드 execution 루프가 주기적으로(설정 간격) 수행:
+1. dispatch: `find_pending_for_dispatch`(status pending_* AND `broker_order_id IS NULL`, `FOR UPDATE SKIP LOCKED`) → `BrokerPort.submit_order` → `mark_dispatched(broker_order_id)`(멱등 가드). 거부 시 `pending_buy→idle` / `pending_sell→holding` 롤백.
+2. poll: `list_dispatched_pending`(broker_order_id NOT NULL) → `BrokerPort.poll_fill` → 체결 시 `pending_buy→holding`(avg_price/qty) / `pending_sell→closed`(+재진입), 거부 시 롤백. 전이 후 `clear_dispatch`.
+3. reconcile(재기동): 서빙 전 `list_dispatched_pending` 재폴링으로 크래시 후 복구(중복 주문 0). 미디스패치(broker_order_id NULL) 슬롯은 다음 dispatch 가 1회만 송신.
+
+- 모든 슬롯 쓰기는 SlotService(advisory lock) 단일 경로(불변식 A). 브로커 주문/취소는 BrokerPort 단일 세션만(불변식 B).
+- 어댑터: paper(결정적 async 더블) / KIS(모의투자 검증, 실계좌 게이팅).
+
 ## Shared Components
 
 - SlotRepository Protocol :: 저장소 추상화. 구현체(InMemorySlotRepository, 향후 PostgreSQLSlotRepository)를 주입.
@@ -93,3 +103,4 @@
 - 2026-06-03 :: bootstrap-baseline 으로 초기 흐름 baseline 생성(slot 도메인 in-process API 흐름 기준).
 - 2026-06-03 :: BAT-001 이식 완료 반영 — preallocate/transit 흐름이 `trex_core.domain.slot` 실제 코드로 구현됨(REQ-004). 영속화/CLI 흐름은 여전히 미구현(범위 밖).
 - 2026-06-03 :: BAT-002 — 데몬 lifecycle + 매수/매도 intent HTTP 흐름 추가, Primary Runtime=daemon+library(REQ-005~009). 브로커 집행/safety floor 흐름은 후속 Discovery.
+- 2026-06-04 :: BAT-004 — 브로커 집행 레이어 반영(BrokerPort/paper·KIS 어댑터, execution 루프, broker_order_id 실행큐·멱등, reconciliation) (REQ-011~015).