Reapply "feat(accessibility): implement centralized screen reader layout (#9263)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

packages/cli/src/ui/layouts/DefaultAppLayout.tsx

@@ -0,0 +1,36 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type React from 'react';
+import { Box } from 'ink';
+import { Notifications } from '../components/Notifications.js';
+import { MainContent } from '../components/MainContent.js';
+import { DialogManager } from '../components/DialogManager.js';
+import { Composer } from '../components/Composer.js';
+import { ExitWarning } from '../components/ExitWarning.js';
+import { useUIState } from '../contexts/UIStateContext.js';
+
+export const DefaultAppLayout: React.FC = () => {
+  const uiState = useUIState();
+
+  return (
+    <Box flexDirection="column" width="90%">
+      <MainContent />
+
+      <Box flexDirection="column" ref={uiState.mainControlsRef}>
+        <Notifications />
+
+        {uiState.dialogsVisible ? (
+          <DialogManager addItem={uiState.historyManager.addItem} />
+        ) : (
+          <Composer />
+        )}
+
+        <ExitWarning />
+      </Box>
+    </Box>
+  );
+};