fix: Handle App objects in eval and graph endpoints

src/google/adk/cli/adk_web_server.py

@@ -966,7 +966,12 @@ async def run_eval(
               status_code=400, detail=f"Eval set `{eval_set_id}` not found."
           )
 
-        root_agent = self.agent_loader.load_agent(app_name)
+        agent_or_app = self.agent_loader.load_agent(app_name)
+        # Extract root_agent if we loaded an App
+        if isinstance(agent_or_app, App):
+          root_agent = agent_or_app.root_agent
+        else:
+          root_agent = agent_or_app
 
         eval_case_results = []
 
@@ -1305,7 +1310,12 @@ async def get_event_graph(
 
       function_calls = event.get_function_calls()
       function_responses = event.get_function_responses()
-      root_agent = self.agent_loader.load_agent(app_name)
+      agent_or_app = self.agent_loader.load_agent(app_name)
+      # Extract root_agent if we loaded an App
+      if isinstance(agent_or_app, App):
+        root_agent = agent_or_app.root_agent
+      else:
+        root_agent = agent_or_app
       dot_graph = None
       if function_calls:
         function_call_highlights = []