refactor: Reorganize docs folder structure for clarity and version management (PR 3c)

Reorganize documentation following AGENTS.md v16.0 governance (traceability, reproducibility):

Structure changes:
- CURRENT/ (new)
  ├─ 00~08.md (v16.0 standards, renamed for clarity)
  └─ CATALOGS/ (9 CSV files: WBS, decision log, debt register, matrices, catalogs)

- LEGACY/ (new, read-only archives)
  ├─ v11/ (original baseline + hardening analysis)
  ├─ v12~v15/ (.gitkeep + README for future archiving)

- DECISIONS/ (new, ready for ADR usage)
- TEMPLATES/ (existing, unchanged)

Deletions (consolidated into CURRENT/):
- v16_0/ folder (files migrated)
- hardening/ folder (contents → LEGACY/v11/)
- Root-level v11 files (00~07.md, CSV)

Renames (for clarity):
- 00_EXECUTIVE_REFERENCE_IMPLEMENTATION.md → 00_EXECUTIVE.md
- 01_BRUTAL_ROLE_AUDIT.md → 01_ROLE_AUDIT.md
- 02_FRONTEND_ADAPTER_CRUD_STANDARD.md → 02_FE_ADAPTER.md
- 03_BACKEND_DATA_SCHEDULER_STANDARD.md → 03_BE_DATA.md
- 04_ALGORITHM_MODEL_GOVERNANCE.md → 04_ALGORITHM.md
- 05_PROCESS_VIBE_DEBT_CONTROL.md → 05_PROCESS_VIBE_DEBT.md
- 06_VALIDATION_TRUTH.md → 06_VALIDATION.md
- 07_PACKAGE_ATTACHMENT_POLICY.md → 07_PACKAGE_POLICY.md

Updates:
- docs/INDEX.md (complete rewrite with navigation)
- LEGACY/ folders with README + .gitkeep

Benefits:
✅ Clear version management (v16.0 is active, v11~v15 read-only)
✅ No version mixing in root
✅ CURRENT/ as single point of reference for active docs
✅ CATALOGS/ consolidates all data matrices
✅ LEGACY/ preserves history without clutter
✅ Traceability: decision log, tech debt, WBS all linked
✅ DECISIONS/ ready for ADR pattern (future use)

Sync with root:
- CLAUDE.md references: docs/CURRENT/, docs/INDEX.md ✅
- AGENTS.md references: docs/CURRENT/, traceability ✅
- README.md: Document guide links updated ✅

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

docs/LEGACY/v11/05_TECH_DEBT_REGISTER.csv

@@ -0,0 +1,8 @@
+DebtId,Title,RiskClass,Evidence,Impact,Owner,Secondary,Created,Due,Remediation,ExitTest,Priority,Decision
+TD-001,Python 원시데이터·환경 lock 부재,Data/Model,source manifest warning,재현성 상실,Quant Lead,Data Lead,2026-08-01,S0,manifest+lock+container,clean-room replay hash,P1,Fix
+TD-002,Scalar position과 lot cycle 혼합,Model,source v12_positions,보호선·재진입 왜곡,BE Lead,Quant Lead,2026-08-01,S2,Lot/Cycle state model,property+golden,P1,Fix
+TD-003,KR capital-floor overlay 비용 상수,Model/Data,portfolio_backtest global cost,KR 결과 왜곡,Quant Lead,QA Lead,2026-08-01,S0,cost parameter/FeeSchedule,cost sensitivity diff,P1,Fix
+TD-004,기업행사 추정 소급조정,Data,load_kr inferred integer rescale,가격·ATR 왜곡,Data Lead,DBA,2026-08-01,S2,official CA master,CA golden reconcile,P1,Fix
+TD-005,정책 코드 중복,Engineering,v11/v12/fast,의미 drift,BE Lead,Quant Lead,2026-08-01,S2,single policy core,contract/golden,P2,Fix
+TD-006,FE lockfile 미생성,Engineering,template baseline,빌드 비결정성,FE Lead,DevOps,2026-08-01,G0,pnpm-lock commit,CI frozen install,P2,Fix
+TD-007,Read Model rebuild 미구현,Operations,initial template,화면 stale/recovery,Data Lead,SRE,2026-08-01,S6,projection version+rebuild,disaster rebuild test,P2,Defer