fix: pass display_name when creating agent with identity (#739)

When deploying with --agent-identity, the setup_agent_identity function
was only passing identity_type to the initial create call, resulting in
agents being created with empty display names. Now includes display_name
in the config to ensure the agent is properly named from the start.

Author: eliasecchig

agent_starter_pack/deployment_targets/agent_engine/python/{{cookiecutter.agent_directory}}/app_utils/deploy.py

@@ -164,7 +164,10 @@ def setup_agent_identity(client: Any, project: str, display_name: str) -> Any:
     """Create agent with identity and grant required IAM roles."""
     click.echo(f"\n🔧 Creating agent identity for: {display_name}")
     agent = client.agent_engines.create(
-        config={"identity_type": IdentityType.AGENT_IDENTITY}
+        config={
+            "identity_type": IdentityType.AGENT_IDENTITY,
+            "display_name": display_name,
+        }
     )
 
     roles = [