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>

spec/40_final_decision_packet_contract.yaml

@@ -0,0 +1,22 @@
+schema_version: final_decision_packet_contract.v4
+formula_id: FINAL_DECISION_PACKET_V4
+purpose: Single packet source of truth for renderer and low-capability LLM output.
+sections:
+  - executive
+  - portfolio
+  - ticker
+  - risk
+  - execution
+  - performance
+  - data_quality
+provenance_requirements:
+  source_path: required
+  json_pointer: required
+  formula_id: required
+  input_hash: required
+  freshness_status: required
+  display_value: required
+render_policy:
+  packet_only: true
+  direct_temp_reads: forbidden
+  numeric_calculation_in_renderer: forbidden