docs(rag): add domain model and original research input

chunking/docs/README.md

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+# Insurance RAG System Documentation
+
+This directory contains architecture decision records (ADRs) for the Insurance RAG System migration from ChromaDB to Qdrant.
+
+## Quick Links
+
+| ADR | Title | Status |
+|-----|-------|--------|
+| [0001](adr/0001-single-collection-with-metadata.md) | Single Collection with Metadata Filtering | Accepted |
+| [0002](adr/0002-chunking-strategy.md) | Hybrid Chunking Strategy | Accepted |
+| [0003](adr/0003-dual-embedding-strategy.md) | Dual Embedding Model Strategy | Accepted |
+| [0004](adr/0004-reranking-strategy.md) | Dual Reranking Strategy | Accepted |
+| [0005](adr/0005-retrieval-evaluation-framework.md) | Retrieval Evaluation Framework | Accepted |
+| [0006](adr/0006-qdrant-deployment.md) | Qdrant Docker Deployment | Accepted |
+| [0007](adr/0007-hybrid-search.md) | Hybrid Search (Dense + Sparse) | Accepted |
+| [0008](adr/0008-metadata-schema.md) | Metadata Schema | Accepted |
+| [0009](adr/0009-ingestion-pipeline.md) | API-Based Continuous Ingestion | Accepted |
+| [0010](adr/0010-query-pipeline.md) | Full-Context Query Pipeline | Accepted |
+| [0011](adr/0011-inference-infrastructure.md) | Ollama Inference on RTX 3090 | Accepted |
+| [0012](adr/0012-observability-auth.md) | Langfuse Observability + API Key Auth | Accepted |
+
+## Architecture Overview
+
+### Problem Context
+
+The current system uses ~30 collections in ChromaDB, requiring query classification before retrieval. Misclassification leads to irrelevant results with no recovery path. Insurance domains are semantically similar, making classification non-trivial.
+
+### Key Constraints
+
+1. **Infrastructure Instability** — Iran's internet blackouts (up to 90 days) require fully offline capability
+2. **Bilingual Content** — Persian (Farsi) and English documents and queries
+
+### Core Decisions
+
+| Decision Point | Choice | Rationale |
+|----------------|--------|-----------|
+| Collection Strategy | Single collection + metadata filtering | Eliminates classification failure mode |
+| Chunking | Hybrid: semantic for unstructured, row-by-row for tabular | Markdown-first pipeline |
+| Embeddings | Dual: OpenAI (online) + Nomic (offline) | Resilience during blackouts |
+| Reranking | Dual: Cohere (online) + BGE (offline) | Precision across domains |
+| Vector DB | Qdrant Docker | Fully on-prem, excellent filtered search |
+| Search | Hybrid: dense + sparse (BM25) | Exact term matching + semantic similarity |
+| Inference | Ollama + Qwen 2.5 on RTX 3090 | Local bilingual LLM |
+| Observability | Langfuse | Full tracing and access control |
+
+## Related Documents
+
+- [Domain Model (CONTEXT.md)](../CONTEXT.md) — Glossary, constraints, and architecture decisions summary
+- [Original Grilling Input](../raw/001.md) — Research request that drove these decisions