feat(agent): add opt-in push notifications

web/src/pwa.ts

@@ -1,12 +1,19 @@
+export async function ensureServiceWorker(): Promise<ServiceWorkerRegistration> {
+  const registration = await navigator.serviceWorker.register("/sw.js", { updateViaCache: "none" });
+  // ready can otherwise remain pending forever after an install failure.
+  return new Promise((resolve, reject) => {
+    const timeout = setTimeout(() => reject(new Error("The notification worker did not become ready. Reload and try again.")), 15000);
+    void navigator.serviceWorker.ready.then(ready => { clearTimeout(timeout); resolve(ready); }, () => {
+      clearTimeout(timeout); reject(new Error("The notification worker is unavailable."));
+    });
+    void registration.update().catch(() => undefined);
+  });
+}
+
 export function registerServiceWorker() {
   if (!import.meta.env.PROD || !("serviceWorker" in navigator)) return;
 
   window.addEventListener("load", () => {
-    void navigator.serviceWorker
-      .register("/sw.js", { updateViaCache: "none" })
-      .then((registration) => registration.update())
-      .catch((error: unknown) => {
-        console.warn("Sybil service worker registration failed", error);
-      });
+    void ensureServiceWorker().catch(() => undefined);
   });
 }