docs: friendly guide + concepts + tutorial + docs index

Add 4 new documents aimed at different audiences:

- docs/GUIDE.md — friendly overview with zero jargon. Explains what
  Synaptic Memory is, why it exists, how knowledge graphs work, and
  the 3-pillar design (code as data, BYO, zero-LLM indexing). Good
  for a first encounter.

- docs/CONCEPTS.md — deep dive into 3rd-gen GraphRAG, the 9-step
  search pipeline, graph structure (node kinds, edge kinds, weights),
  multi-turn agent design, and why SQLite was chosen as the default.
  For engineers who want to understand the "why".

- docs/TUTORIAL.md — 30-minute hands-on walkthrough. CSV single
  table → multi-table with FK → structured tools → full agent loop
  → MCP server → quality tuning → custom benchmarks. Copy-paste
  runnable code all the way through.

- docs/README.md — index file with purpose-driven links. Points
  readers to the right doc based on their goal (first-time user,
  engineer, evaluator, etc.).

Also added a Documentation section to README.md and README.ko.md
linking to all docs/*.md files.

Author: SonAIengine

README.ko.md

@@ -253,6 +253,17 @@ StorageBackend (Protocol)
 
 ---
 
+## 문서
+
+| 문서 | 내용 |
+|------|------|
+| [docs/GUIDE.md](docs/GUIDE.md) | 친절한 전체 안내서 (처음 접하는 사람용) |
+| [docs/TUTORIAL.md](docs/TUTORIAL.md) | 30분 단계별 실습 |
+| [docs/CONCEPTS.md](docs/CONCEPTS.md) | 3세대 GraphRAG + 파이프라인 심화 |
+| [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md) | 신경망 영감 초기 설계 |
+| [docs/COMPARISON.md](docs/COMPARISON.md) | GraphRAG/LightRAG와 비교 |
+| [docs/ROADMAP.md](docs/ROADMAP.md) | 향후 로드맵 |
+
 ## 개발
 
 ```bash

README.md

@@ -253,6 +253,17 @@ Agent tools (29) → MCP server → LLM agent
 
 ---
 
+## Documentation
+
+| Doc | What it is |
+|-----|-----------|
+| [docs/GUIDE.md](docs/GUIDE.md) | Friendly intro — what/why/how, zero jargon |
+| [docs/TUTORIAL.md](docs/TUTORIAL.md) | 30-minute hands-on walkthrough |
+| [docs/CONCEPTS.md](docs/CONCEPTS.md) | 3rd-gen GraphRAG + pipeline internals |
+| [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md) | Original neural-inspired design |
+| [docs/COMPARISON.md](docs/COMPARISON.md) | vs GraphRAG / LightRAG / LazyGraphRAG |
+| [docs/ROADMAP.md](docs/ROADMAP.md) | Future plans |
+
 ## Dev
 
 ```bash