feat(slot): dcy-021 포지션 사이징 — 보유 슬롯 증액·부분 매도 (BAT-031)

자산 영구 슬롯(dcy-020)의 수량 가변 전제 위에 보유 포지션 수량 조정 구현.
명령형 계약(전략이 cash+quantity 로 qty+price 계산), core 는 실행 substrate,
수량 정본 = 브로커 잔고 재동기화로 "주문 수량 vs 보유 수량" 충돌 해소(별도 필드 없음).

- state.py: holding→pending_buy 전이 추가(증액) → 13 transitions (REQ-057)
- service.py: PENDING_SELL 진입 qty=caller as-is(None=전량 sentinel, 값=부분 주문) (REQ-062)
- intents.py: 증액 admission(holding 슬롯 매수=increase, M 캡 미적용), SellIntent.qty 부분 매도 (REQ-061)
- execution.py: _balance_map; 매도 dispatch=브로커잔고(전량)/min(주문,잔고)(부분);
  매수 체결 avg_price 가중평균+브로커 정본 resync; 매도 체결 잔고>0→holding/0→inactive;
  증액 롤백 holding 복귀 (REQ-066/062)
- messaging_handlers.py: sell payload qty 파싱(부분 매도)
- baseline 4문서(data-model/runtime-flows/interface-contract/project-structure) 정합 (REQ-067)

검증: 단위 378 / 통합(PG+RabbitMQ) 422 passed, ruff clean. run-the-app 사이징 e2e:
매수 10@1000 → 증액 +5@1200 → 15@1066.67(가중평균) → 부분 매도 6 → 9@1066.67(cost basis) → 전량→inactive.

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

tests/domain/slot/test_service.py

@@ -300,3 +300,40 @@ class TestAdvisoryLockSerialization:
         )
         elapsed_ms = (time.perf_counter() - t0) * 1000
         assert elapsed_ms < 50.0, f"transition took {elapsed_ms:.2f} ms"
+
+
+# ----------------------------------------------------------------------------
+# dcy-021: position sizing — increase transition + INACTIVE/sell qty semantics
+# ----------------------------------------------------------------------------
+class TestPositionSizing:
+    def _holding(self, service, repo, qty=10.0, avg=1000.0):
+        slot = _seed(repo)[0]
+        service.transit_slot(slot.slot_id, SlotState.INACTIVE, SlotState.PENDING_BUY,
+                             reason="buy", actor="t", symbol="005930", qty=qty)
+        return service.transit_slot(slot.slot_id, SlotState.PENDING_BUY, SlotState.HOLDING,
+                                    reason="filled", actor="t", avg_price=avg, qty=qty)
+
+    def test_holding_to_pending_buy_increase_preserves_avg(self, service, repo):
+        """증액 pending: HOLDING→PENDING_BUY 가 허용되고 avg_price(가중평균용)가 보존된다."""
+        h = self._holding(service, repo)
+        inc = service.transit_slot(h.slot_id, SlotState.HOLDING, SlotState.PENDING_BUY,
+                                   reason="position_increase", actor="t", qty=5, limit_price=1200)
+        assert inc.status is SlotState.PENDING_BUY
+        assert inc.avg_price == 1000.0   # preserved for weighted-average at fill
+        assert inc.qty == 5              # order qty during pending
+        assert inc.limit_price == 1200
+
+    def test_full_sell_pending_clears_qty_to_none(self, service, repo):
+        """전량 매도(qty 미지정) PENDING_SELL 진입 시 slot.qty = None('전량' sentinel)."""
+        h = self._holding(service, repo)
+        ps = service.transit_slot(h.slot_id, SlotState.HOLDING, SlotState.PENDING_SELL,
+                                  reason="sell", actor="t")  # qty omitted
+        assert ps.status is SlotState.PENDING_SELL and ps.qty is None
+
+    def test_partial_sell_pending_records_order_qty(self, service, repo):
+        """부분 매도 PENDING_SELL 진입 시 slot.qty = 주문 수량."""
+        h = self._holding(service, repo)
+        ps = service.transit_slot(h.slot_id, SlotState.HOLDING, SlotState.PENDING_SELL,
+                                  reason="sell", actor="t", qty=4, limit_price=1100)
+        assert ps.qty == 4 and ps.limit_price == 1100
+        assert ps.avg_price == 1000.0  # cost basis preserved

tests/domain/slot/test_state.py

@@ -59,6 +59,7 @@ def test_slot_advisory_lock_id_is_instance_scoped():
         (SlotState.INACTIVE, SlotState.PENDING_BUY),
         (SlotState.PENDING_BUY, SlotState.HOLDING),
         (SlotState.PENDING_BUY, SlotState.INACTIVE),
+        (SlotState.HOLDING, SlotState.PENDING_BUY),    # dcy-021 increase
         (SlotState.HOLDING, SlotState.PENDING_SELL),
         (SlotState.PENDING_SELL, SlotState.INACTIVE),
         (SlotState.PENDING_SELL, SlotState.HOLDING),
@@ -83,7 +84,6 @@ def test_allowed_transition(from_state: SlotState, to_state: SlotState):
         (SlotState.INACTIVE, SlotState.HOLDING),
         (SlotState.INACTIVE, SlotState.PENDING_SELL),
         (SlotState.HOLDING, SlotState.INACTIVE),
-        (SlotState.HOLDING, SlotState.PENDING_BUY),
         (SlotState.PENDING_BUY, SlotState.PENDING_SELL),
         (SlotState.PENDING_SELL, SlotState.PENDING_BUY),
         # error has restricted exits — only inactive and holding
@@ -103,5 +103,5 @@ def test_self_loops_are_not_allowed():
 
 
 def test_allowed_transitions_set_size():
-    """6 base + 4 to-error + 2 operator-resolve = 12."""
-    assert len(ALLOWED_TRANSITIONS) == 12
+    """7 base (incl. dcy-021 holding→pending_buy) + 4 to-error + 2 operator-resolve = 13."""
+    assert len(ALLOWED_TRANSITIONS) == 13