chore(vendor): import pi 0.85.1

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: d981de1229ef899957bbe968bc8dcda02a21f477

third_party/pi/packages/client/src/promise.ts

@@ -0,0 +1,16 @@
+export interface PromiseResolvers<T> {
+	promise: Promise<T>;
+	resolve(value: T | PromiseLike<T>): void;
+	reject(reason?: unknown): void;
+}
+
+/** Remove in favor of `Promise.withResolvers()` when the repository's TypeScript lib baseline moves to ES2024. */
+export function createPromiseResolvers<T>(): PromiseResolvers<T> {
+	let resolve!: PromiseResolvers<T>["resolve"];
+	let reject!: PromiseResolvers<T>["reject"];
+	const promise = new Promise<T>((resolvePromise, rejectPromise) => {
+		resolve = resolvePromise;
+		reject = rejectPromise;
+	});
+	return { promise, resolve, reject };
+}