feat(ui): Introduce useUI Hook and UIContext (#5488)

Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/cli/src/ui/contexts/ConfigContext.tsx

@@ -0,0 +1,18 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import React, { useContext } from 'react';
+import { type Config } from '@google/gemini-cli-core';
+
+export const ConfigContext = React.createContext<Config | undefined>(undefined);
+
+export const useConfig = () => {
+  const context = useContext(ConfigContext);
+  if (context === undefined) {
+    throw new Error('useConfig must be used within a ConfigProvider');
+  }
+  return context;
+};