test(stammbaum): tidyTree packs multiple roots left-to-right (#724)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/person/genealogy/layout/tidyTree.test.ts

@@ -97,3 +97,22 @@ describe('tidyTree — contour nesting', () => {
 		);
 	});
 });
+
+describe('tidyTree — multi-root packing', () => {
+	it('packs multiple roots left-to-right with no overlap', () => {
+		// A real Stammbaum is a forest of ~50 roots, not a single tree — this is
+		// the dominant compactness win. Three roots of differing shapes.
+		const r1 = node('r1', [leaf('r1a'), leaf('r1b')]);
+		const r2 = leaf('r2');
+		const r3 = node('r3', [leaf('r3a')]);
+		const roots = [r1, r2, r3];
+		const x = layoutForest(roots, GAP);
+
+		expectNoOverlap(x, roots, GAP);
+		// Roots keep input order left-to-right.
+		expect(x.get('r1')!).toBeLessThan(x.get('r2')!);
+		expect(x.get('r2')!).toBeLessThan(x.get('r3')!);
+		// Forest is normalised so the leftmost edge is at 0.
+		expect(Math.min(...x.values())).toBe(0);
+	});
+});