test(stammbaum): fix #718 tab-order test for tidy-tree layout (#724)

The #718 keyboard-tab-order test hardcoded the visual order
['Eugenie','Walter','Clara','Hans'] on the assumption that buildLayout
sorts each generation alphabetically. #724 replaced that with the
tidy-tree layout, which orders a couple's run by structural ownership
(earliest birth year, then a deterministic id tie-break) — so Walter
(id …a1) now owns the run and Eugenie renders to his right.

Both PRs were green independently; the stale assertion only surfaced
once #718 and #724 landed together on main. Correct the expected reading
order to ['Walter','Eugenie','Clara','Hans'] and refresh the now-wrong
'alphabetical' comment. The companion self-validating test (DOM order ==
sorted by y,x) already guarded the real property, so only the hardcoded
assertion needed updating.

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

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

@@ -1099,9 +1099,11 @@ describe('StammbaumTree keyboard tab order (#718)', () => {
 	const CLARA = '00000000-0000-0000-0000-0000000000a3';
 	const HANS = '00000000-0000-0000-0000-0000000000a4';
 
-	// Walter ↔ Eugenie (gen 0); their children Clara + Hans (gen 1). buildLayout
-	// sorts each generation alphabetically, so the deterministic visual order is
-	// Eugenie, Walter (top row) then Clara, Hans (next row).
+	// Walter ↔ Eugenie (gen 0); their children Clara + Hans (gen 1). The tidy-tree
+	// layout (#724) orders a couple's run by structural ownership (earliest birth
+	// year, then a deterministic id tie-break), not alphabetically — with no birth
+	// years here Walter (id …a1) owns the run and Eugenie sits to his right. So the
+	// deterministic visual order is Walter, Eugenie (top row) then Clara, Hans.
 	const FAMILY_EDGES = [
 		{
 			id: 'sp',
@@ -1171,7 +1173,7 @@ describe('StammbaumTree keyboard tab order (#718)', () => {
 		});
 
 		// Top generation left-to-right, then next generation left-to-right.
-		expect(nodeLabelsInDomOrder()).toEqual(['Eugenie', 'Walter', 'Clara', 'Hans']);
+		expect(nodeLabelsInDomOrder()).toEqual(['Walter', 'Eugenie', 'Clara', 'Hans']);
 	});
 
 	it('orders tab stops by rendered position regardless of input order', () => {