perf(cli): cache loadSettings to reduce redundant disk I/O at startup (#21521)

packages/cli/src/ui/hooks/useExtensionUpdates.test.tsx

@@ -24,7 +24,10 @@ import {
 } from '../../config/extensions/update.js';
 import { ExtensionUpdateState } from '../state/extensions.js';
 import { ExtensionManager } from '../../config/extension-manager.js';
-import { loadSettings } from '../../config/settings.js';
+import {
+  loadSettings,
+  resetSettingsCacheForTesting,
+} from '../../config/settings.js';
 
 vi.mock('os', async (importOriginal) => {
   const mockedOs = await importOriginal<typeof os>();
@@ -59,6 +62,7 @@ describe('useExtensionUpdates', () => {
   let extensionManager: ExtensionManager;
 
   beforeEach(() => {
+    resetSettingsCacheForTesting();
     vi.mocked(loadAgentsFromDirectory).mockResolvedValue({
       agents: [],
       errors: [],