feat: 리밸런싱 엔진 V1 + GAS 버그 수정 (2026-06-13)

주요 변경:
- tools/build_rebalance_engine_v1.py: REBALANCE_ENGINE_V1 신규
  * account_snapshot 직접 합산(_build_snap_position_map) → 소수주 분리 행 병합
  * 레짐 소스 macro.REGIME_PRELIM 최우선 (GAS 와 동일)
- src/gas_adapter_parts/gdf_06_rebalance.gs: runRebalanceSheet_() 신규
  * Logger.log / getSpreadsheet_() 로 run_all 연동 수정
- src/gas_adapter_parts/gdc_01_fetch_fundamentals.gs
  * _mergePositionRecord_(): 소수주 중복 행 합산 신규
  * parseInt → parseFloat (qty, availQty)
- src/gas_adapter_parts/gdf_01_price_metrics.gs
  * 미보유 종목 SELL_READY → WATCH_EXIT_SIGNAL
- spec/41_release_dag.yaml: build_rebalance_sheet 노드 추가 (step_count 63)
- spec/51_formula_lifecycle_registry.yaml: REBALANCE_ENGINE_V1 등록

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/sell_case.yaml

@@ -0,0 +1,21 @@
+case_id: EX_SELL_001
+type: SELL
+input_summary:
+  confirmed_holding_quantity: 120
+  price_status: "OK"
+  flow20d_status: "OK"
+  trend_status: "20일선 이탈"
+  risk_trigger: "relative_weakness_exit"
+expected_output:
+  investment_action: "SELL"
+  required_fields:
+    - "account"
+    - "ticker"
+    - "limit_price_krw"
+    - "quantity"
+    - "rationale"
+  prohibited_if_missing:
+    - "confirmed_holding_quantity"
+  rule_ids_used:
+    - "HF003_HOLDINGS_REQUIRED_FOR_SELL_QTY"
+    - "spec/exit/stop_loss.yaml:stop_loss.relative_weakness_exit"