feat: Update default embedding model to text-embedding-3-small

Replace outdated text-embedding-ada-002 with the newer, more efficient
text-embedding-3-small model as the default embedder. The new model
offers better performance and is more cost-effective.

Updated:
- config/config.yaml: Changed default model
- README.md: Updated documentation to reflect new default

mcp_server/README.md

@@ -107,7 +107,7 @@ The MCP server comes with sensible defaults:
 - **Transport**: HTTP (accessible at `http://localhost:8000/mcp/`)
 - **Database**: Kuzu (in-memory, no external dependencies required)
 - **LLM**: OpenAI with model gpt-4.1
-- **Embedder**: OpenAI text-embedding-ada-002
+- **Embedder**: OpenAI text-embedding-3-small
 
 ### Database Configuration
 

mcp_server/config/config.yaml

@@ -41,7 +41,7 @@ llm:
 
 embedder:
   provider: "openai"  # Options: openai, azure_openai, gemini, voyage
-  model: "text-embedding-ada-002"
+  model: "text-embedding-3-small"
   dimensions: 1536
   
   providers: