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/49_refactor_methodology_contract.yaml

@@ -0,0 +1,19 @@
+schema_version: refactor_methodology_contract.v1
+principles:
+  - QEDD: Quant Evidence-Driven Deterministic Development
+  - Contract-First: YAML/Schema before implementation
+  - Python Canonical: Logic in src/quant_engine, GAS is thin adapter
+  - No LLM Math: LLM copies harness values with provenance
+authority_order:
+  - spec/*.yaml
+  - runtime/active_artifact_manifest.yaml
+  - Temp/final_decision_packet_active.json
+  - governance/rules/*.yaml
+file_policy:
+  source: [md, yaml, py, gs]
+  runtime: [json, jsonl, schema.json]
+do_done:
+  - Release DAG PASS
+  - No SKIPPED in release mode
+  - Zero architecture boundary violations
+  - 100% number provenance coverage