feat(Card): add optional title prop with uppercase monospace header

When a title string is provided, renders an uppercase monospace h3 header
with a subtle border separator above the card body. Children are wrapped
in a padded body div when title is present; without title, children render
directly as before (no breaking change).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/design-system/primitives/Card/Card.module.css

@@ -11,3 +11,22 @@
 .accent-warning { border-top: 3px solid var(--warning); }
 .accent-error   { border-top: 3px solid var(--error); }
 .accent-running { border-top: 3px solid var(--running); }
+
+.titleHeader {
+  padding: 12px 16px;
+  border-bottom: 1px solid var(--border-subtle);
+}
+
+.titleText {
+  font-size: 11px;
+  text-transform: uppercase;
+  font-family: var(--font-mono);
+  font-weight: 600;
+  color: var(--text-secondary);
+  letter-spacing: 0.5px;
+  margin: 0;
+}
+
+.body {
+  padding: 16px;
+}

src/design-system/primitives/Card/Card.test.tsx

@@ -0,0 +1,49 @@
+import { describe, it, expect } from 'vitest'
+import { render, screen } from '@testing-library/react'
+import { Card } from './Card'
+
+describe('Card', () => {
+  it('renders children', () => {
+    render(<Card>Hello world</Card>)
+    expect(screen.getByText('Hello world')).toBeInTheDocument()
+  })
+
+  it('renders title when provided', () => {
+    render(<Card title="Status">Content</Card>)
+    expect(screen.getByText('Status')).toBeInTheDocument()
+  })
+
+  it('does not render title header when title is omitted', () => {
+    const { container } = render(<Card>Content</Card>)
+    expect(container.querySelector('h3')).toBeNull()
+  })
+
+  it('wraps children in body div when title is provided', () => {
+    render(<Card title="Status"><span>Content</span></Card>)
+    const content = screen.getByText('Content')
+    expect(content.parentElement).toHaveClass('body')
+  })
+
+  it('renders with accent and title together', () => {
+    const { container } = render(
+      <Card accent="success" title="Health">Content</Card>,
+    )
+    const card = container.firstChild as HTMLElement
+    expect(card).toHaveClass('accent-success')
+    expect(screen.getByText('Health')).toBeInTheDocument()
+    expect(screen.getByText('Content')).toBeInTheDocument()
+  })
+
+  it('accepts className prop', () => {
+    const { container } = render(<Card className="custom">Content</Card>)
+    const card = container.firstChild as HTMLElement
+    expect(card).toHaveClass('custom')
+  })
+
+  it('renders children directly when no title (no wrapper div)', () => {
+    const { container } = render(<Card><span>Direct child</span></Card>)
+    const card = container.firstChild as HTMLElement
+    const span = screen.getByText('Direct child')
+    expect(span.parentElement).toBe(card)
+  })
+})

src/design-system/primitives/Card/Card.tsx

@@ -4,15 +4,25 @@ import type { ReactNode } from 'react'
 interface CardProps {
   children: ReactNode
   accent?: 'amber' | 'success' | 'warning' | 'error' | 'running' | 'none'
+  title?: string
   className?: string
 }
 
-export function Card({ children, accent = 'none', className }: CardProps) {
+export function Card({ children, accent = 'none', title, className }: CardProps) {
   const classes = [
     styles.card,
     accent !== 'none' ? styles[`accent-${accent}`] : '',
     className ?? '',
   ].filter(Boolean).join(' ')
 
-  return <div className={classes}>{children}</div>
+  return (
+    <div className={classes}>
+      {title && (
+        <div className={styles.titleHeader}>
+          <h3 className={styles.titleText}>{title}</h3>
+        </div>
+      )}
+      {title ? <div className={styles.body}>{children}</div> : children}
+    </div>
+  )
 }