feat(web): set up Storybook (preview + MSW + stories for real components)

web/src/components/ui/button.stories.tsx

@@ -0,0 +1,35 @@
+import type { Meta, StoryObj } from '@storybook/react-vite'
+import { expect } from 'storybook/test'
+
+import { Button } from './button'
+
+const meta = {
+  component: Button,
+  tags: ['ai-generated'],
+} satisfies Meta<typeof Button>
+
+export default meta
+type Story = StoryObj<typeof meta>
+
+export const Default: Story = {
+  args: { children: 'Save' },
+  play: async ({ canvas }) => {
+    const button = canvas.getByRole('button', { name: /save/i })
+    await expect(button).toHaveAttribute('data-slot', 'button')
+  },
+}
+
+export const Outline: Story = {
+  args: { variant: 'outline', children: 'Cancel' },
+}
+
+export const Destructive: Story = {
+  args: { variant: 'destructive', children: 'Delete' },
+}
+
+export const Disabled: Story = {
+  args: { children: 'Save', disabled: true },
+  play: async ({ canvas }) => {
+    await expect(canvas.getByRole('button', { name: /save/i })).toBeDisabled()
+  },
+}