Don't allow #builtin relations to be asserted or queried

[robsimmons]

This works and it shouldn't, logging [ [ [ 1n, 2n, 3n ] ] ]

import { Dusa } from "https://unpkg.com/[email protected]/lib/client.js";
const dusa = new Dusa("#builtin INT_PLUS plus");
dusa.assert({ name: "plus", args: [1, 2], value: 3 });
console.log([...dusa].map(sol => [...sol.lookup("plus")]));