Expect the snackbar host to stay after an actioned toast closes

Plan step 32. Since actions.md ACT-02 the host is the permanent polite live
region, in the page before any message and after the last, so the test
that waited for it to disappear once Undo ran could never pass. It now
waits for the toast to go and checks the host stays.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

tests/Browser/CommunicationTest.php

@@ -78,7 +78,8 @@ it('runs a toast\'s action and dismisses it', function () {
 
     $page->click('[x-data="materialSnackbar"] button:has-text("Undo")')
         ->assertScript('window.__undone === true')
-        ->assertScript(SNACKBAR.' === null');
+        ->assertScript(TOAST.' === null')
+        ->assertScript(SNACKBAR.' !== null');
 });
 
 it('does not let a toast dismissed early cut the next one short', function () {