fix(activity): drop Cancel job from a job that had ended before Activity opened

Since #289 the Activity list removed an item's actions only when they were
isConnected. On the first render the item is not in the page yet, so a job
that had already ended when Activity opened kept its "Cancel job" (and a
running job's progress was moved after its actions, then back). The list
now asks parentNode instead. The review spec "a scan job with review items
offers Review metadata in Activity" failed on this before the change
(Expected 0 buttons on a finished job, Received 1) and passes after it.

web/js/workspace/activity.mjs

@@ -164,18 +164,20 @@ function itemFor(job, scope) {
         chip.textContent = state;
         detail.textContent = jobDetail(next);
         const running = next.state === 'running';
+        // parentNode, not isConnected: on the first render the item is not in the page yet, so a job that had already
+        // ended when Activity opened kept its Cancel job (and a running one's progress moved after its actions).
         if (running) {
             progress.value = next.progress;
             progress.textContent = `${next.progress}%`;
             progress.setAttribute('aria-label', `${next.title} progress`);
-            if (!progress.isConnected) item.insertBefore(progress, actions.isConnected ? actions : null);
+            if (!progress.parentNode) item.insertBefore(progress, actions.parentNode ? actions : null);
         } else {
             progress.remove();
         }
         // Truth rule: a job that cannot be cancelled (a held legacy-page job) shows no Cancel job.
         if (running && next.cancellable) {
-            if (!actions.isConnected) item.append(actions);
-        } else if (actions.isConnected) {
+            if (!actions.parentNode) item.append(actions);
+        } else if (actions.parentNode) {
             // A focused Cancel job that goes away hands its focus to the item's title link, never to the page body.
             if (actions.contains(document.activeElement)) link.focus();
             actions.remove();