task: add langgraph retriever tool

src/tools/design_retriever.py

@@ -0,0 +1,25 @@
+from typing import Dict, Optional
+from langchain.tools import BaseTool
+from chains.design_rag import DesignRAG
+from pydantic import Field
+import json
+
+class DesignRetrieverTool(BaseTool):
+    """Tool for retrieving similar designs based on requirements."""
+    
+    name: str = "design_retriever"
+    description: str = "Retrieves similar designs based on style requirements"
+    rag: DesignRAG = Field(description="Design RAG system for retrieving similar designs")
+    
+    def __init__(self, rag: DesignRAG):
+        """Initialize the tool with a DesignRAG instance."""
+        super().__init__(rag=rag)
+    
+    def _run(self, requirements: Dict, num_examples: int = 3) -> str:
+        """Sync version - not used but required by BaseTool"""
+        raise NotImplementedError("Use async version")
+    
+    async def _arun(self, requirements: Dict, num_examples: int = 3) -> str:
+        """Retrieve similar designs based on requirements"""
+        print(f"Retrieving {num_examples} similar designs")
+        return await self.rag.query_similar_designs(requirements, num_examples)