feat(staples): add StapleChip component with aria-pressed toggle and focus ring

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/onboarding/StapleChip.svelte

@@ -0,0 +1,20 @@
+<script lang="ts">
+  let { name, selected, onToggle }: {
+    name: string;
+    selected: boolean;
+    onToggle: (value: boolean) => void;
+  } = $props();
+</script>
+
+<button
+  type="button"
+  aria-pressed={selected}
+  onclick={() => onToggle(!selected)}
+  class="inline-flex text-[12px] font-medium px-[12px] py-[6px] rounded-full border cursor-pointer
+    focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-[var(--green-light)]
+    {selected
+      ? 'bg-[var(--green-tint)] border-[var(--green-light)] text-[var(--green-dark)]'
+      : 'bg-[var(--color-surface)] border-[var(--color-border)] text-[var(--color-text-muted)]'}"
+>
+  {name}
+</button>

frontend/src/lib/onboarding/StapleChip.test.ts

@@ -0,0 +1,45 @@
+import { describe, it, expect, vi } from 'vitest';
+import { render, screen } from '@testing-library/svelte';
+import { userEvent } from '@testing-library/user-event';
+import StapleChip from './StapleChip.svelte';
+
+describe('StapleChip', () => {
+	it('renders a button with the ingredient name', () => {
+		render(StapleChip, { props: { name: 'Olivenöl', selected: false, onToggle: vi.fn() } });
+		expect(screen.getByRole('button', { name: 'Olivenöl' })).toBeInTheDocument();
+	});
+
+	it('is aria-pressed="false" when unselected', () => {
+		render(StapleChip, { props: { name: 'Olivenöl', selected: false, onToggle: vi.fn() } });
+		expect(screen.getByRole('button', { name: 'Olivenöl' })).toHaveAttribute('aria-pressed', 'false');
+	});
+
+	it('is aria-pressed="true" when selected', () => {
+		render(StapleChip, { props: { name: 'Olivenöl', selected: true, onToggle: vi.fn() } });
+		expect(screen.getByRole('button', { name: 'Olivenöl' })).toHaveAttribute('aria-pressed', 'true');
+	});
+
+	it('calls onToggle with true when unselected chip is clicked', async () => {
+		const user = userEvent.setup();
+		const onToggle = vi.fn();
+		render(StapleChip, { props: { name: 'Olivenöl', selected: false, onToggle } });
+
+		await user.click(screen.getByRole('button', { name: 'Olivenöl' }));
+		expect(onToggle).toHaveBeenCalledWith(true);
+	});
+
+	it('calls onToggle with false when selected chip is clicked', async () => {
+		const user = userEvent.setup();
+		const onToggle = vi.fn();
+		render(StapleChip, { props: { name: 'Olivenöl', selected: true, onToggle } });
+
+		await user.click(screen.getByRole('button', { name: 'Olivenöl' }));
+		expect(onToggle).toHaveBeenCalledWith(false);
+	});
+
+	it('has a visible focus ring class for keyboard accessibility', () => {
+		render(StapleChip, { props: { name: 'Olivenöl', selected: false, onToggle: vi.fn() } });
+		const btn = screen.getByRole('button', { name: 'Olivenöl' });
+		expect(btn.className).toContain('focus-visible:outline');
+	});
+});