Function graph_node_from_entity 

pub fn graph_node_from_entity<T: Entity>(
    ctx: &UserContext,
    entity: T,
) -> Result<GraphNode, RuntimeError>

Convert a typed entity into a GraphNode tree.

This only requires metadata (entity descriptors) from the UserContext, not the database executor. It is the standalone equivalent of [EntityDataService::graph_node_from_entity].