test(transcription): update markAllReviewed non-OK test to expect throw

The function now throws instead of silently returning on failure.
Update the test name and assertion to match the new behaviour, and
verify blocks remain unchanged after the error.

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

frontend/src/lib/document/transcription/useTranscriptionBlocks.svelte.test.ts

@@ -259,12 +259,15 @@ describe('createTranscriptionBlocks.markAllReviewed', () => {
 		expect(ctrl.blocks.every((b) => b.reviewed)).toBe(true);
 	});
 
-	it('is a no-op when PUT returns non-OK', async () => {
+	it('throws and leaves blocks unchanged when PUT returns non-OK', async () => {
 		const fetchImpl = vi.fn(async (url: RequestInfo | URL, init?: RequestInit) => {
 			const u = url.toString();
 			const method = init?.method ?? 'GET';
 			if (u.includes('/review-all') && method === 'PUT') {
-				return new Response('', { status: 500 });
+				return new Response(JSON.stringify({ code: 'INTERNAL_ERROR' }), {
+					status: 500,
+					headers: { 'Content-Type': 'application/json' }
+				});
 			}
 			return new Response(JSON.stringify([baseBlock({ id: 'b-1', reviewed: false })]), {
 				status: 200,
@@ -274,7 +277,7 @@ describe('createTranscriptionBlocks.markAllReviewed', () => {
 
 		const ctrl = createTranscriptionBlocks({ documentId: () => 'doc-1', fetchImpl });
 		await ctrl.load();
-		await ctrl.markAllReviewed();
+		await expect(ctrl.markAllReviewed()).rejects.toThrow('INTERNAL_ERROR');
 		expect(ctrl.blocks[0].reviewed).toBe(false);
 	});
 });