change directory to working direct before saving graph html file

src/rag/graph_rag.py

@@ -1220,13 +1220,13 @@ class GraphRAG:
         net.options["layout"] = {"improvedLayout": True}
         net.options["interaction"] = {"dragNodes": True}
 
-        file_path = os.path.join(os.getenv("WRITABLE_DIR", "/tmp"), "temp_graph.html")
-        net.save_graph(file_path)
+        os.chdir(os.getenv("WRITABLE_DIR", "/tmp"))
+        net.save_graph("temp_graph.html")
 
-        with open(file_path, "r", encoding="utf-8") as f:
+        with open("temp_graph.html", "r", encoding="utf-8") as f:
             html_str = f.read()
             
-        # os.remove(file_path)
+        os.remove("temp_graph.html")
         return html_str
 
     def verify_graph_integrity(self):