Function entity 

pub fn entity(name: impl Into<String>) -> EntityValue

Create an EntityValue for a named entity with default (unknown) agreement features. Chain builder methods to set gender, number, etc.

use prosaic_core::{ctx, entity, Value};
use prosaic_core::agreement::Gender;

let c = ctx! {
    user: entity("Alice").fem().sing().defined(),
    service: entity("UserService"),  // features stay Unknown — English default
};
match c.get("user").unwrap() {
    Value::Entity { name, .. } => assert_eq!(name, "Alice"),
    _ => panic!(),
}