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)

src/components/ui/button.tsx

@@ -0,0 +1,59 @@
+/**
+ * Button Component
+ * Based on shadcn/ui button
+ */
+import * as React from 'react';
+import { Slot } from '@radix-ui/react-slot';
+import { cva, type VariantProps } from 'class-variance-authority';
+import { cn } from '@/lib/utils';
+
+const buttonVariants = cva(
+  'inline-flex items-center justify-center whitespace-nowrap rounded-md text-sm font-medium ring-offset-background transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50',
+  {
+    variants: {
+      variant: {
+        default: 'bg-primary text-primary-foreground hover:bg-primary/90',
+        destructive:
+          'bg-destructive text-destructive-foreground hover:bg-destructive/90',
+        outline:
+          'border border-input bg-background hover:bg-accent hover:text-accent-foreground',
+        secondary:
+          'bg-secondary text-secondary-foreground hover:bg-secondary/80',
+        ghost: 'hover:bg-accent hover:text-accent-foreground',
+        link: 'text-primary underline-offset-4 hover:underline',
+      },
+      size: {
+        default: 'h-10 px-4 py-2',
+        sm: 'h-9 rounded-md px-3',
+        lg: 'h-11 rounded-md px-8',
+        icon: 'h-10 w-10',
+      },
+    },
+    defaultVariants: {
+      variant: 'default',
+      size: 'default',
+    },
+  }
+);
+
+export interface ButtonProps
+  extends React.ButtonHTMLAttributes<HTMLButtonElement>,
+    VariantProps<typeof buttonVariants> {
+  asChild?: boolean;
+}
+
+const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(
+  ({ className, variant, size, asChild = false, ...props }, ref) => {
+    const Comp = asChild ? Slot : 'button';
+    return (
+      <Comp
+        className={cn(buttonVariants({ variant, size, className }))}
+        ref={ref}
+        {...props}
+      />
+    );
+  }
+);
+Button.displayName = 'Button';
+
+export { Button, buttonVariants };