feat(slot): BAT-029 M2(a)/M3 — holding 불일치 reconcile + slots 단일 뷰 (dcy-020/REQ-062·063)

- REQ-062 divergence: list_holding_slots(protocol+in_memory+PG) +
  reconcile_core_holdings(A=코어 holding/broker0→error, C=수량 불일치→warning,
  B=broker 보유/코어 없음→warning; 자동 청산 없음 issue #15). snapshot_scheduler
  자산 중심 모드에서 best-effort 호출, daemon slot_service 배선.
- REQ-063: slot_to_dict 에 universe_detached(retired_at) 추가 — slots 단일 뷰 tombstone 표시.
- 신규 테스트: test_holding_divergence(4).

M2(b) 청산 수량 브로커 정본(execution dispatch)은 라이브 집행 변경 → BAT-δ carry-over.

검증: 단위 393 passed / 36 skipped, PG-gated 18 passed, ruff clean. legacy 무파손.
REQ-061/062/063 Approved 유지(γ 경로 도입 검증; default 전환·M2(b) 는 BAT-δ).

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

trex_core/application/reconciliation.py

@@ -12,10 +12,62 @@ import logging
 
 from trex_core.application.broker_port import BrokerPort
 from trex_core.application.portfolio import SnapshotStore
+from trex_core.domain.slot.state import SlotState
 
 _log = logging.getLogger(__name__)
 
 
+def reconcile_core_holdings(*, slot_repo, slot_service, broker: BrokerPort,
+                           instance_key: str) -> dict[str, str]:
+    """dcy-020 / REQ-062 (BAT-029): surface core-slot holding ↔ broker divergence.
+
+    Broker balance is the reconcile ground truth. Decisions (no silent auto-fix,
+    no auto-liquidation — issue #15):
+    - A. core holding but broker flat (qty 0)  -> slot to `error` + WARN (operator resolve)
+    - C. both hold but qty differs             -> WARN (mirror is non-authoritative)
+    - B. broker holds, no core holding slot    -> WARN (unmanaged position)
+    Returns {key: 'error'|'qty_warning'|'ok'|'unmanaged_warning'} for telemetry.
+    (Liquidation qty = broker authoritative in execution dispatch is BAT-δ.)"""
+    broker_qty: dict[str, int] = {
+        item.symbol: int(item.hldg_qty) for item in broker.get_balance()
+    }
+    decisions: dict[str, str] = {}
+    matched: set[str] = set()
+    for slot in slot_repo.list_holding_slots(instance_key):
+        sym = slot.symbol
+        matched.add(sym)
+        bq = broker_qty.get(sym, 0)
+        if bq == 0:  # A — phantom holding
+            try:
+                slot_service.transit_slot(
+                    slot.slot_id, SlotState.HOLDING, SlotState.ERROR,
+                    reason="reconcile_mismatch:broker_flat", actor="reconcile",
+                )
+                decisions[str(slot.slot_id)] = "error"
+                _log.warning(
+                    "core holding but broker flat: slot=%s symbol=%s -> error",
+                    slot.slot_id, sym,
+                )
+            except Exception:  # noqa: BLE001 - never let reconcile crash the loop
+                _log.exception("failed to error-quarantine slot %s", slot.slot_id)
+        elif slot.qty is not None and int(slot.qty) != bq:  # C — qty mismatch
+            decisions[str(slot.slot_id)] = "qty_warning"
+            _log.warning(
+                "qty mismatch: slot=%s symbol=%s core=%s broker=%d (mirror non-authoritative)",
+                slot.slot_id, sym, slot.qty, bq,
+            )
+        else:
+            decisions[str(slot.slot_id)] = "ok"
+    for sym, bq in broker_qty.items():  # B — unmanaged broker position
+        if bq > 0 and sym not in matched:
+            decisions[f"broker:{sym}"] = "unmanaged_warning"
+            _log.warning(
+                "broker holds %s qty=%d with no core holding slot (unmanaged position)",
+                sym, bq,
+            )
+    return decisions
+
+
 def reconcile_positions(*, store: SnapshotStore, broker: BrokerPort) -> dict[str, str]:
     """Run one reconciliation pass.