feat(core-B): 운영자 sync/verify CLI + cold-start onboarding (BAT-051, REQ-105/106, PR #32)

dcy-034 마지막 조각. sync(슬롯 qty←브로커+warning해제+OQ-A 전이엣지+FR-7 평단seed)/verify(C 재대조·강제해제없음). core-A QC minor 2건 정리 동봉. QC(opus) PASS, 683 passed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VHtM5Ws1HKCKQ4JGi6GRb5

trex_core/application/ports.py

@@ -47,3 +47,20 @@ class IntentRecord:
     status: str
     slot_id: Optional[UUID]
     reason: Optional[str]
+
+
+class PortfolioHubCostBasisPort(Protocol):
+    """FR-7 (dcy-034 / REQ-105): portfolio-hub WAC (weighted average cost) read port.
+
+    Wraps `GET /v1/portfolios/{id}/holdings/cost-basis` from portfolio-hub REQ-043.
+    When unavailable or when the portfolio has no holding, implementations return None.
+    sync() degrades gracefully: None => skip avg_price seed + WARN log.
+    """
+
+    def get_cost_basis(self, portfolio_id: str) -> Optional[float]:
+        """Return the weighted average cost (WAC) for the portfolio's current holding.
+
+        Returns None when the portfolio has no holding, the endpoint is unavailable,
+        or any error occurs. The caller must handle None as a graceful-degrade signal.
+        """
+        ...