fix: critical bugs and hardening from validation audit

- Fix infinite loop in chunker _hard_split when overlap >= max_size
- Fix tag filter false positives by quoting tag values in ChromaDB query
- Fix score boost semantics (additive → multiplicative) to stay within 0-1 range
- Add error handling and type hints to all API routes
- Update README with proper project documentation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -1,3 +1,67 @@
-# ATODrive
+# AtoCore
 
-ATODrive project repository
+Personal context engine that enriches LLM interactions with durable memory, structured context, and project knowledge.
+
+## Quick Start
+
+```bash
+pip install -e .
+uvicorn src.atocore.main:app --port 8100
+```
+
+## Usage
+
+```bash
+# Ingest markdown files
+curl -X POST http://localhost:8100/ingest \
+  -H "Content-Type: application/json" \
+  -d '{"path": "/path/to/notes"}'
+
+# Build enriched context for a prompt
+curl -X POST http://localhost:8100/context/build \
+  -H "Content-Type: application/json" \
+  -d '{"prompt": "What is the project status?", "project": "myproject"}'
+
+# CLI ingestion
+python scripts/ingest_folder.py --path /path/to/notes
+```
+
+## API Endpoints
+
+| Method | Path | Description |
+|--------|------|-------------|
+| POST | /ingest | Ingest markdown file or folder |
+| POST | /query | Retrieve relevant chunks |
+| POST | /context/build | Build full context pack |
+| GET | /health | Health check |
+| GET | /debug/context | Inspect last context pack |
+
+## Architecture
+
+```
+FastAPI (port 8100)
+  ├── Ingestion: markdown → parse → chunk → embed → store
+  ├── Retrieval: query → embed → vector search → rank
+  ├── Context Builder: retrieve → boost → budget → format
+  ├── SQLite (documents, chunks, memories, projects, interactions)
+  └── ChromaDB (vector embeddings)
+```
+
+## Configuration
+
+Set via environment variables (prefix `ATOCORE_`):
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| ATOCORE_DEBUG | false | Enable debug logging |
+| ATOCORE_PORT | 8100 | Server port |
+| ATOCORE_CHUNK_MAX_SIZE | 800 | Max chunk size (chars) |
+| ATOCORE_CONTEXT_BUDGET | 3000 | Context pack budget (chars) |
+| ATOCORE_EMBEDDING_MODEL | paraphrase-multilingual-MiniLM-L12-v2 | Embedding model |
+
+## Testing
+
+```bash
+pip install -e ".[dev]"
+pytest
+```