Polish Feynman harness and stabilize Pi web runtime

src/system/promise-polyfill.ts

@@ -0,0 +1,26 @@
+type PromiseWithResolvers<T> = {
+	promise: Promise<T>;
+	resolve: (value: T | PromiseLike<T>) => void;
+	reject: (reason?: unknown) => void;
+};
+
+declare global {
+	interface PromiseConstructor {
+		withResolvers?<T>(): PromiseWithResolvers<T>;
+	}
+}
+
+if (typeof Promise.withResolvers !== "function") {
+	Promise.withResolvers = function withResolvers<T>(): PromiseWithResolvers<T> {
+		let resolve!: (value: T | PromiseLike<T>) => void;
+		let reject!: (reason?: unknown) => void;
+		const promise = new Promise<T>((res, rej) => {
+			resolve = res;
+			reject = rej;
+		});
+		return { promise, resolve, reject };
+	};
+}
+
+export {};
+