test(web): add Vitest+RTL tests for 15 design-system presentational components

Covers Badge, Divider, EmptyState, Numeric, PriceDelta, Signal, Skeleton,
StatusChip, Surface, StatCard, KpiCard, DensityToggle, Footer, MarketIndex,
CompactHeader — rendering, variants, props, a11y attributes, className merging.

All 1139 web tests pass. Zustand persist store mocked for DensityToggle to
avoid jsdom localStorage incompatibility.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/components/design-system/__tests__/divider.spec.tsx

@@ -0,0 +1,41 @@
+import { render, screen } from '@testing-library/react';
+import { describe, expect, it } from 'vitest';
+import { Divider } from '../divider';
+
+describe('Divider', () => {
+  it('renders with role="separator"', () => {
+    render(<Divider />);
+    expect(screen.getByRole('separator')).toBeInTheDocument();
+  });
+
+  it('defaults to horizontal orientation', () => {
+    render(<Divider data-testid="d" />);
+    expect(screen.getByTestId('d')).toHaveAttribute('aria-orientation', 'horizontal');
+  });
+
+  it('renders vertical orientation', () => {
+    render(<Divider data-testid="d" orientation="vertical" />);
+    expect(screen.getByTestId('d')).toHaveAttribute('aria-orientation', 'vertical');
+    expect(screen.getByTestId('d')).toHaveClass('h-full', 'w-px');
+  });
+
+  it('applies strong variant class', () => {
+    render(<Divider data-testid="d" strong />);
+    expect(screen.getByTestId('d')).toHaveClass('bg-border-strong');
+  });
+
+  it('applies default border class without strong', () => {
+    render(<Divider data-testid="d" />);
+    expect(screen.getByTestId('d')).toHaveClass('bg-border');
+  });
+
+  it('horizontal adds h-px and w-full', () => {
+    render(<Divider data-testid="d" orientation="horizontal" />);
+    expect(screen.getByTestId('d')).toHaveClass('h-px', 'w-full');
+  });
+
+  it('merges custom className', () => {
+    render(<Divider data-testid="d" className="my-custom" />);
+    expect(screen.getByTestId('d')).toHaveClass('my-custom');
+  });
+});