fix: вернуть регистрацию activeXHR (onXHR) для отмены загрузки + тесты чистых функций

upload/frontend/test_upload_layer2.mjs

@@ -87,6 +87,16 @@ async function testPutToVmTimeout() {
   console.log('  putToVm timeout: ok');
 }
 
+async function testPutToVmOnXHR() {
+  let registered = null;
+  const p = putToVm(new File(['abc'], 'a.txt'), 'https://vm/tok_0', { onXHR(x) { registered = x; } });
+  assert.ok(registered, 'onXHR должен получить XHR для отмены');
+  registered.status = 200;
+  registered.onload();
+  await p;
+  console.log('  putToVm onXHR регистрация: ok');
+}
+
 // ── uploadViaVM ──
 async function testUploadViaVMSuccess() {
   installFetch(() => ({ ok: true, json: async () => ({ ok: true, session: 'sid123', count: 2 }) }));
@@ -172,6 +182,7 @@ const TESTS = [
   ['putToVm HTTP error', testPutToVmHttpError],
   ['putToVm network error', testPutToVmNetworkError],
   ['putToVm timeout', testPutToVmTimeout],
+  ['putToVm onXHR', testPutToVmOnXHR],
   ['uploadViaVM success', testUploadViaVMSuccess],
   ['uploadViaVM PUT error', testUploadViaVMPutError],
   ['uploadViaVM POST error', testUploadViaVMPostError],