feat: wire async app flows for checkout x mentions signed playback and queued generation

test/engine.test.js

@@ -180,3 +180,25 @@ test("round-trips state snapshot across engine restart", () => {
   assert.equal(engine2.getAsset(created.job.assetId).articleTitle, "Snap");
   assert.equal(engine2.checkAudioAccess(created.job.assetId, "u1").allowed, true);
 });
+
+test("updateAsset patches stored asset metadata", () => {
+  const engine = createEngine();
+  engine.topUpCredits("u1", 5, "topup-update-asset");
+  const created = engine.processMention({
+    mentionPostId: "m-update-asset",
+    callerUserId: "u1",
+    parentPost: {
+      id: "p-update-asset",
+      authorId: "author",
+      article: { id: "a-update", title: "T", body: "hello" },
+    },
+  });
+
+  const updated = engine.updateAsset(created.job.assetId, {
+    storageKey: "audio/real-file.mp3",
+    sizeBytes: 12345,
+  });
+
+  assert.equal(updated.storageKey, "audio/real-file.mp3");
+  assert.equal(updated.sizeBytes, 12345);
+});