Remove unused Async type

src/state/Async.ts

@@ -1,59 +0,0 @@
-/*
-Copyright 2025 New Vector Ltd.
-
-SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
-Please see LICENSE in the repository root for full details.
-*/
-
-import { catchError, from, map, type Observable, of, startWith } from "rxjs";
-
-/**
- * Data that may need to be loaded asynchronously.
- *
- * This type is for when you need to represent the current state of an operation
- * involving Promises as **immutable data**. See the async$ function below.
- */
-export type Async<A> =
-  | { state: "loading" }
-  | { state: "error"; value: Error }
-  | { state: "ready"; value: A };
-
-export const loading: Async<never> = { state: "loading" };
-export function error(value: Error): Async<never> {
-  return { state: "error", value };
-}
-
-export function ready<A>(value: A): Async<A> {
-  return { state: "ready", value };
-}
-
-/**
- * Turn a Promise into an Observable async value. The Observable will have the
- * value "loading" while the Promise is pending, "ready" when the Promise
- * resolves, and "error" when the Promise rejects.
- */
-export function async$<A>(promise: Promise<A>): Observable<Async<A>> {
-  return from(promise).pipe(
-    map(ready),
-    startWith(loading),
-    catchError((e: unknown) =>
-      of(error((e as Error) ?? new Error("Unknown error"))),
-    ),
-  );
-}
-
-/**
- * If the async value is ready, apply the given function to the inner value.
- */
-export function mapAsync<A, B>(
-  async: Async<A>,
-  project: (value: A) => B,
-): Async<B> {
-  return async.state === "ready" ? ready(project(async.value)) : async;
-}
-
-export function unwrapAsync<A>(fallback: A): (async: Async<A>) => A {
-  return (async: Async<A>) => {
-    return async.state === "ready" ? async.value : fallback;
-  };
-}