ci: add a source and artifact cloud readiness gate

Co-Authored-By: Paperclip <noreply@paperclip.ing>

scripts/cloud-readiness.mjs

@@ -0,0 +1,46 @@
+#!/usr/bin/env node
+import { pathToFileURL } from "node:url";
+import { imageExists, packageExists, versionFor } from "./preview-artifacts.mjs";
+
+/** Read-only availability gate. Deployment still resolves and pins artifacts. */
+export async function waitForCloudArtifacts(sha, {
+  fetchImpl = fetch,
+  now = () => performance.now(),
+  sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms)),
+  timeoutMs = 30 * 60_000,
+  intervalMs = 20_000,
+  log = console.log,
+} = {}) {
+  const version = versionFor(sha);
+  if (!Number.isFinite(timeoutMs) || timeoutMs <= 0 || !Number.isFinite(intervalMs) || intervalMs <= 0) {
+    throw new Error("Cloud readiness requires positive finite timeout and poll interval.");
+  }
+  const deadline = now() + timeoutMs;
+  let previous;
+  let missing = ["image", "shared", "db"];
+  while (now() < deadline) {
+    // Recheck every artifact on the successful poll. Only an explicit 404
+    // means publication is pending; identity errors and upstream outages fail.
+    const results = await Promise.all([
+      imageExists(sha, fetchImpl),
+      packageExists("@paperclipai/shared", sha, fetchImpl),
+      packageExists("@paperclipai/db", sha, fetchImpl),
+    ]);
+    missing = ["image", "shared", "db"].filter((_, index) => !results[index]);
+    if (missing.length === 0) {
+      log(`Cloud artifacts available for ${sha}: verified image and exact-source migrator ${version}.`);
+      return { version: 1, sha, packageVersion: version };
+    }
+    const state = missing.join(", ");
+    if (state !== previous) log(`Waiting for cloud artifacts for ${sha}: ${state}.`);
+    previous = state;
+    const remaining = deadline - now();
+    if (remaining > 0) await sleep(Math.min(intervalMs, remaining));
+  }
+  throw new Error(`Cloud artifacts timed out for ${sha}; missing: ${missing.join(", ")}.`);
+}
+
+if (process.argv[1] && import.meta.url === pathToFileURL(process.argv[1]).href) {
+  try { await waitForCloudArtifacts(process.argv[2]); }
+  catch (error) { console.error(error.message); process.exitCode = 1; }
+}