feat: add the dsh-superagent research prototype

tests/fixtures/async.ts

@@ -0,0 +1,18 @@
+/** Async coordination helpers for tests. */
+import { vi } from 'vitest'
+
+/** Create an externally resolvable promise. */
+export function deferred<T = void>() {
+  let resolve!: (value: T) => void
+  let reject!: (error: unknown) => void
+  const promise = new Promise<T>((res, rej) => { resolve = res; reject = rej })
+  return { promise, resolve, reject }
+}
+/** Observe whether a promise has settled without awaiting it. */
+export function track<T>(promise: Promise<T>) {
+  const state = { settled: false, error: undefined as unknown, promise }
+  promise.then(() => { state.settled = true }, (error: unknown) => { state.settled = true; state.error = error })
+  return state
+}
+export const sleep = (ms: number) => new Promise(resolve => setTimeout(resolve, ms))
+export const waitUntil = (check: () => boolean, timeout = 3000) => vi.waitFor(() => { if (!check()) throw new Error('not yet') }, { timeout, interval: 2 })