Introduce IDE mode installer (#4877)

packages/cli/src/ui/hooks/slashCommandProcessor.test.ts

@@ -16,6 +16,7 @@ vi.mock('@google/gemini-cli-core', async (importOriginal) => {
     ...original,
     logSlashCommand,
     SlashCommandEvent,
+    getIdeInstaller: vi.fn().mockReturnValue(null),
   };
 });
 
@@ -23,11 +24,16 @@ const { mockProcessExit } = vi.hoisted(() => ({
   mockProcessExit: vi.fn((_code?: number): never => undefined as never),
 }));
 
-vi.mock('node:process', () => ({
-  default: {
+vi.mock('node:process', () => {
+  const mockProcess = {
     exit: mockProcessExit,
-  },
-}));
+    platform: 'test-platform',
+  };
+  return {
+    ...mockProcess,
+    default: mockProcess,
+  };
+});
 
 const mockBuiltinLoadCommands = vi.fn();
 vi.mock('../../services/BuiltinCommandLoader.js', () => ({