swarm ui: a stored claude login closes the dialog and shows a toast

The login dialog stayed open with a success line after the code was
accepted, though nothing is left to do in it. It now closes and a toast
says the login is stored. The toast is a new swarm-ui primitive: a short
note raised with showToast, rendered by a ToastHost at the app root, gone
after a few seconds or on click.

frontend/packages/swarm-ui/src/App.tsx

@@ -16,6 +16,7 @@ import { JobsPage } from "./pages/JobsPage.js";
 import { ReportsPage } from "./pages/reports/ReportsPage.js";
 import { StartPage } from "./pages/StartPage.js";
 import { Panel } from "./ui/panel/Panel.js";
+import { ToastHost } from "./ui/toast/Toast.js";
 
 // An address from before the tabs were folded together: replace it with the
 // tab that holds the page now, query kept.
@@ -34,6 +35,7 @@ function NotFound() {
 export function App() {
   return (
     <Router hook={useGuardedLocation}>
+      <ToastHost />
       <Shell>
         <Switch>
           <Route path="/" component={StartPage} />