Add LightRAG MCP integration for RAG-enhanced AI reasoning
This commit integrates LightRAG (Retrieval-Augmented Generation) MCP server
support into CHORUS, enabling graph-based knowledge retrieval to enrich AI
reasoning and context resolution.
## New Components
1. **LightRAG Client** (pkg/mcp/lightrag_client.go)
- HTTP client for LightRAG MCP server
- Supports 4 query modes: naive, local, global, hybrid
- Health checking, document insertion, context retrieval
- 277 lines with comprehensive error handling
2. **Integration Tests** (pkg/mcp/lightrag_client_test.go)
- Unit and integration tests
- Tests all query modes and operations
- 239 lines with detailed test cases
3. **SLURP Context Enricher** (pkg/slurp/context/lightrag.go)
- Enriches SLURP context nodes with RAG data
- Batch processing support
- Knowledge base building over time
- 203 lines
4. **Documentation** (docs/LIGHTRAG_INTEGRATION.md)
- Complete integration guide
- Configuration examples
- Usage patterns and troubleshooting
- 350+ lines
## Modified Components
1. **Configuration** (pkg/config/config.go)
- Added LightRAGConfig struct
- Environment variable support (5 variables)
- Default configuration with hybrid mode
2. **Reasoning Engine** (reasoning/reasoning.go)
- GenerateResponseWithRAG() - RAG-enriched generation
- GenerateResponseSmartWithRAG() - Smart model + RAG
- SetLightRAGClient() - Client configuration
- Non-fatal error handling (graceful degradation)
3. **Runtime Initialization** (internal/runtime/shared.go)
- Automatic LightRAG client setup
- Health check on startup
- Integration with reasoning engine
## Configuration
Environment variables:
- CHORUS_LIGHTRAG_ENABLED (default: false)
- CHORUS_LIGHTRAG_BASE_URL (default: http://127.0.0.1:9621)
- CHORUS_LIGHTRAG_TIMEOUT (default: 30s)
- CHORUS_LIGHTRAG_API_KEY (optional)
- CHORUS_LIGHTRAG_DEFAULT_MODE (default: hybrid)
## Features
- ✅ Optional and non-blocking (graceful degradation)
- ✅ Four query modes for different use cases
- ✅ Context enrichment for SLURP system
- ✅ Knowledge base building over time
- ✅ Health monitoring and error handling
- ✅ Comprehensive tests and documentation
## Testing
LightRAG server tested at http://127.0.0.1:9621
- Health check: ✅ Passed
- Query operations: ✅ Tested
- Integration points: ✅ Verified
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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