- Add native tool handlers export for embedding in other MCP servers
- Add SpaceContext for multi-tenant isolation (internal/hidden feature)
- Add embedded mode support in DuckDBMCPServer
- Add selective exports with controlled access through export maps
- Bump version to 0.2.0
- Update README with embedding documentation

This allows deposium_MCPs to directly use DuckDB tools without duplication,
fixing the 'Unknown tool: query_duckdb' error while laying foundation for
future space-aware federation and SLM pilot features.