Download the whole app build behind a loading page

In production, a page request without the running build's cookie gets a
small loading page instead of the app. It downloads every file in
.bunext/public (listed at /build-info.json) into that build's cache,
checks they are all there, hands over to a new service worker waiting
behind an older one, sets the cookie and reloads. The service worker
then serves the app's code from the cache, so later visits load it from
the device.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/types/index.ts

@@ -697,6 +697,15 @@ export type BotTextModel = {
     provider_name: string;
 };
 
+/**
+ * One build's `.bunext/public` files, downloaded by the service worker
+ * before the app runs (`grabPrecacheManifest`).
+ */
+export type PrecacheManifest = {
+    build_id: string;
+    files: string[];
+};
+
 export type PagePropsType = {
     user?: User | null;
     user_types?: BUN_SQLITE_COBBLE_USER_TYPES[] | null;