test(variety): add boundary tests for VarietyScoreHero (score=0,4,7,10)

Addresses QA concern: boundary values (0, 4, 7, 9, 10) now have
explicit tests covering description labels and aria-valuenow.

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

frontend/src/lib/planner/VarietyScoreHero.test.ts

@@ -40,4 +40,35 @@ describe('VarietyScoreHero', () => {
 		render(VarietyScoreHero, { props: { score: 2.1 } });
 		expect(screen.getByTestId('score-description').textContent).toContain('Unzureichend');
 	});
+
+	it('shows "Unzureichend" for score = 0 (boundary)', () => {
+		render(VarietyScoreHero, { props: { score: 0 } });
+		expect(screen.getByTestId('score-description').textContent).toContain('Unzureichend');
+	});
+
+	it('renders score 0 in score-value for score = 0', () => {
+		render(VarietyScoreHero, { props: { score: 0 } });
+		expect(screen.getByTestId('score-value').textContent).toContain('0');
+	});
+
+	it('renders 0-width progress bar for score = 0', () => {
+		render(VarietyScoreHero, { props: { score: 0 } });
+		const bar = screen.getByRole('progressbar');
+		expect(bar.getAttribute('aria-valuenow')).toBe('0');
+	});
+
+	it('shows "Ausgezeichnet" for score = 10 (boundary)', () => {
+		render(VarietyScoreHero, { props: { score: 10 } });
+		expect(screen.getByTestId('score-description').textContent).toContain('Ausgezeichnet');
+	});
+
+	it('shows "Verbesserbar" for score = 4 (boundary)', () => {
+		render(VarietyScoreHero, { props: { score: 4 } });
+		expect(screen.getByTestId('score-description').textContent).toContain('Verbesserbar');
+	});
+
+	it('shows "Gut" for score = 7 (boundary)', () => {
+		render(VarietyScoreHero, { props: { score: 7 } });
+		expect(screen.getByTestId('score-description').textContent).toContain('Gut');
+	});
 });