fix(shell): coordinate startup cover and tab stills

packages/shell/src/frame/site.ts

@@ -99,6 +99,8 @@ export type ShellSite = {
   name: string;
   /** The app's name ("wayBetter for X"): the update chip, the brand button, the palette's group. */
   product: string;
+  /** Match native `AppConfig::defer_window_show`: reveal after the first layout reaches native. */
+  deferWindowShow?: boolean;
   /** The app's logo (an image URL): titlebar, the panel tab, the new-tab page, the site chip. */
   logo: string;
   /** The site's home feed: the first tab, and what an account opens beside. */