test(web): use typed JSON responses in updater checks

web/src/lib/utils/app-update.spec.ts

@@ -5,7 +5,7 @@ describe('web update checking', () => {
     ['same', false],
     ['new-build', true],
   ])('compares the deployed build %s', async (version, available) => {
-    const request = vi.fn().mockResolvedValue(new Response(JSON.stringify({ version })));
+    const request = vi.fn().mockResolvedValue(Response.json({ version }));
     expect(await checkWebUpdate('same', request)).toEqual({ version, available });
     expect(request).toHaveBeenCalledWith(
       '/_app/version.json',
@@ -14,9 +14,7 @@ describe('web update checking', () => {
   });
 
   it.each([null, {}, { version: '' }, { version: 42 }])('rejects an invalid version response %j', async (body) => {
-    await expect(
-      checkWebUpdate('same', vi.fn().mockResolvedValue(new Response(JSON.stringify(body)))),
-    ).rejects.toThrow();
+    await expect(checkWebUpdate('same', vi.fn().mockResolvedValue(Response.json(body)))).rejects.toThrow();
   });
 
   it('reports HTTP errors instead of treating them as no updates', async () => {