feat(core): initialize project skeleton with Electron + React + TypeScript

Set up the complete project foundation for ClawX, a graphical AI assistant:

- Electron main process with IPC handlers, menu, tray, and gateway management
- React renderer with routing, layout components, and page scaffolding
- Zustand state management for gateway, settings, channels, skills, chat, and cron
- shadcn/ui components with Tailwind CSS and CSS variable theming
- Build tooling with Vite, electron-builder, and TypeScript configuration
- Testing setup with Vitest and Playwright
- Development configurations (ESLint, Prettier, gitignore, env example)

tests/setup.ts

@@ -0,0 +1,44 @@
+/**
+ * Vitest Test Setup
+ * Global test configuration and mocks
+ */
+import { vi } from 'vitest';
+import '@testing-library/jest-dom';
+
+// Mock window.electron API
+const mockElectron = {
+  ipcRenderer: {
+    invoke: vi.fn(),
+    on: vi.fn(),
+    once: vi.fn(),
+    off: vi.fn(),
+  },
+  openExternal: vi.fn(),
+  platform: 'darwin',
+  isDev: true,
+};
+
+Object.defineProperty(window, 'electron', {
+  value: mockElectron,
+  writable: true,
+});
+
+// Mock matchMedia
+Object.defineProperty(window, 'matchMedia', {
+  writable: true,
+  value: vi.fn().mockImplementation((query) => ({
+    matches: false,
+    media: query,
+    onchange: null,
+    addListener: vi.fn(),
+    removeListener: vi.fn(),
+    addEventListener: vi.fn(),
+    removeEventListener: vi.fn(),
+    dispatchEvent: vi.fn(),
+  })),
+});
+
+// Reset mocks after each test
+afterEach(() => {
+  vi.clearAllMocks();
+});