test(stammbaum): assert connector dimming at the render layer (#703 AC5)

Sara/Elicit flagged that AC5 was proven only at the isConnectorActive
predicate level. Add render-layer assertions: no connector group carries a
dim opacity when nothing is selected, and selecting Vater dims exactly the
vertical feeding the collateral child Tante. Exercises the shared
parent-pair per-child <g opacity> wiring.

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

frontend/src/lib/person/genealogy/StammbaumTree.svelte.test.ts

@@ -965,6 +965,15 @@ describe('StammbaumTree lineage highlight (#703)', () => {
 	}
 	const DIM = String(DIMMED_OPACITY);
 
+	// Connector groups render as direct <svg> children; the node content groups
+	// (also .lineage-fade) are nested inside g[role="button"], so the child
+	// combinator scopes cleanly to connectors.
+	function dimmedConnectorCount(): number {
+		return Array.from(document.querySelectorAll('svg > g.lineage-fade')).filter(
+			(g) => g.getAttribute('opacity') === DIM
+		).length;
+	}
+
 	it('renders every node at full strength when nothing is selected (AC1)', () => {
 		render(StammbaumTree, {
 			nodes: NODES,
@@ -1047,4 +1056,33 @@ describe('StammbaumTree lineage highlight (#703)', () => {
 		});
 		for (const n of NODES) expect(nodeOpacity(n.displayName)).toBeNull();
 	});
+
+	it('leaves every connector at full strength when nothing is selected (AC5)', () => {
+		render(StammbaumTree, {
+			nodes: NODES,
+			edges: EDGES,
+			selectedId: null,
+			panZoom: { x: 0, y: 0, z: 1 },
+			showGutter: false,
+			onSelect: () => {}
+		});
+		expect(dimmedConnectorCount()).toBe(0);
+	});
+
+	it('dims exactly the connector feeding the collateral child at the render layer (AC5)', () => {
+		render(StammbaumTree, {
+			nodes: NODES,
+			edges: EDGES,
+			selectedId: 'vater',
+			panZoom: { x: 0, y: 0, z: 1 },
+			showGutter: false,
+			onSelect: () => {}
+		});
+		// Every connector among the bloodline + spouses stays full strength; only
+		// the vertical joining the active parent pair (Grossvater+Grossmutter) to
+		// the dimmed collateral child (Tante) renders at DIMMED_OPACITY. This proves
+		// the <g opacity> render wiring — not just the isConnectorActive predicate —
+		// and exercises the shared parent-pair per-child path.
+		expect(dimmedConnectorCount()).toBe(1);
+	});
 });