Deliver BAT-002: slot-core daemon + HTTP intent API + PostgreSQL

Implement REQ-005~009 (dcy-002 slice 1) as an onion stack on top of the
BAT-001 pure domain:
- application: IntentService (admission + single-writer transition +
  intent_id idempotency via durable intent_log)
- adapters/persistence: PostgreSQLSlotRepository + PostgreSQLIntentStore +
  trex-core-owned migrations (daily_slot per Appendix A, daily_symbol_entries,
  slot_transition_log, intent_log) + in-memory intent store
- adapters/api: FastAPI /v1 (healthz, intents/buy|sell|{id}, slots, capacity)
- runtime: trex-core-daemon entrypoint with lifespan migrate+preallocate

Verification (against local PostgreSQL 18): 74 passed, ruff clean, domain
import sweep shows zero web/db deps (NFR-1), 20-thread concurrency admits
exactly the idle count (NFR-2), idempotent resubmit causes no double
transition (NFR-3), EXPECTED_SLOT_FIELDS<->information_schema drift test
(realizes dcy-001 OQ-2's deferred DB-side check), and a daemon E2E smoke.

Align all four baseline docs to the new daemon/API/persistence layers.
BAT-002 -> release-candidate; REQ-005~009 -> Implemented. Full async outbox,
broker execution, safety floor, and strategy daemons remain deferred to a
follow-up Discovery.

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

docs/interface-contract.md

@@ -4,9 +4,9 @@
 - Baseline Seed: .stage-pilot/bootstrap/baseline.yaml
 - Status: draft
 - Owner: project maintainers
-- Last Updated (KST): 2026-06-03
-- Source Discovery / Batch: bootstrap-baseline (pre-Discovery)
-- Primary Runtime: library
+- Last Updated (KST): 2026-06-03 (BAT-002)
+- Source Discovery / Batch: bootstrap-baseline (pre-Discovery); HTTP API = dcy-002 / BAT-002
+- Primary Runtime: daemon (HTTP API) + library (slot 도메인)
 
 ## Project Summary
 - trex 제품군의 공용 베이스로, 첫 도메인으로 trex-orbit 의 일일 거래 슬롯 생명주기(slot) 순수 도메인을 storage-agnostic 하게 이식한 코어다.
@@ -19,15 +19,37 @@
 - It is a cross-cutting reference for REQ drafting, batch design, implementation, verification, and handoff.
 
 ## Scope
-- Covers in-process domain-service APIs and the persistence boundary Protocol (library 형태라 외부 HTTP/CLI 표면은 아직 없음).
+- Covers the HTTP `/v1` API(슬롯 코어 데몬, BAT-002), in-process domain-service APIs, and the persistence boundary Protocol.
 - Does not duplicate full business requirements already owned by REQ documents.
 - Does not replace low-level code references or generated API artifacts.
 
 ## Interface Summary
 
+- HTTP `/v1` API :: 슬롯 코어 데몬이 노출, 매수·매도 전략 데몬이 호출(REQ-005/007/008)
 - SlotService :: 슬롯 생명주기 도메인 서비스(전이/사전할당/가용성/재진입 카운트)
 - SlotRepository (Protocol) :: 도메인 ↔ 저장소 경계 계약
 
+## Interface: `HTTP /v1` (슬롯 코어 데몬)
+
+- Type: http-api
+- Consumers / Producers: 매수·매도 전략 데몬(클라이언트) → trex-core 슬롯 코어 데몬(서버). FastAPI+uvicorn.
+- Purpose: 전략이 intent 를 제출하고 holding 스냅샷/capacity 를 조회. 코어가 단독 admission + 슬롯 전이(단일 writer).
+- Stability: experimental (v1, 슬라이스 1)
+
+| 엔드포인트 | 입력 | 출력 | 에러/거부 |
+|---|---|---|---|
+| `GET /v1/healthz` | — | `{status:"ok"}` 200 | — |
+| `POST /v1/intents/buy` | intent_id, trading_date, symbol, qty?, allocated_capital?, entry_price?, strategy_id?, sell_strategy_id?, portfolio_id?, forced_close_at? | `{intent_id, status:admitted|rejected, slot_id?, reason?}` | reject: `no_idle_slot`, `idle_slot_contended` |
+| `POST /v1/intents/sell` | intent_id, slot_id, reason?, sell_strategy_id? | `{intent_id, status, slot_id?, reason?}` | reject: `slot_not_found`, `slot_not_holding:<state>`, `slot_state_changed` |
+| `GET /v1/intents/{intent_id}` | path intent_id | `{intent_id, status, slot_id?, reason?}` | 404 intent not found |
+| `GET /v1/slots?status=&trading_date=` | query | `[SlotSnapshot]` | — |
+| `GET /v1/capacity?trading_date=&total_slots=` | query | `{idle_count, holding_count, pending_count, total_slots, scarcity_ratio}` | — |
+
+### Compatibility / Invariants
+- 멱등: `intent_id` dedup(intent_log UNIQUE gate). at-least-once 재전송에도 슬롯 1회만 전이; 재조회는 `GET /v1/intents/{id}`.
+- 단일 writer: 모든 슬롯 쓰기는 코어의 SlotService(advisory lock)만. 전략은 제안만, 슬롯/브로커 직접 접근 금지.
+- 동기 커밋: 수락 시 admission+전이를 동기 커밋 후 admit/reject 응답(완전 비동기 outbox 는 브로커 Discovery Deferred).
+
 ## Interface: `SlotService`
 
 - Type: internal-service
@@ -111,3 +133,4 @@
 ## Change Log
 
 - 2026-06-03 :: bootstrap-baseline 으로 초기 인터페이스 계약 baseline 생성(SlotService + SlotRepository Protocol).
+- 2026-06-03 :: BAT-002 — HTTP `/v1` API 계약(데몬, 6 엔드포인트) + 멱등/단일writer 불변식 추가(REQ-007/008/009).