feat(ui): back and forward also step through task lists and lists

The open task list and the open list are part of the place in the
browser history; the app's own choice of a first list replaces the
entry. Going back to a task list shows its tasks from memory right away.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/triage/TasksView.tsx

@@ -42,6 +42,7 @@ import { AvatarStack, AvatarPerson } from '../../components/AvatarStack';
 import { CountBadge } from '../../components/CountBadge';
 import { ListSwitcher } from '../../components/ListSwitcher';
 import { isPhoneWidth } from '../../lib/breakpoints';
+import { reportNav, onNavStep, restoringNavPlace } from '../../lib/navHistory';
 import { LivePill } from '../../components/LivePill';
 import { FormSheet } from '../../components/FormSheet';
 import { EmojiIconButton } from '../../components/EmojiIconButton';
@@ -181,7 +182,11 @@ export const TasksView: React.FC<TasksViewProps> = ({
   const [tasks, setTasks] = useState<Thought[]>([]);
   const [taskLists, setTaskLists] = useState<TaskList[]>([]);
   const [selectedListId, setSelectedListIdState] = useState<string>(
-    () => remembered.listId || 'all'
+    () => {
+      // Coming back here by the browser's back/forward: the list of that step
+      const step = restoringNavPlace();
+      return (step?.tab === 'tasks' && step.taskList) || remembered.listId || 'all';
+    }
   );
   const viewMode: ViewMode = viewModes[selectedListId] || 'list';
   // Only Kanban is stored; the list view is the default
@@ -365,6 +370,16 @@ export const TasksView: React.FC<TasksViewProps> = ({
     setSelectedListIdState(id);
   }, []);
 
+  // Switching task lists is a step of the browser history (lib/navHistory.ts)
+  useEffect(() => reportNav({ taskList: selectedListId }), [selectedListId]);
+  useEffect(
+    () =>
+      onNavStep((place) => {
+        if (place.tab === 'tasks' && place.taskList) setSelectedListId(place.taskList);
+      }),
+    [setSelectedListId]
+  );
+
   const onRefreshStatsRef = useRef(onRefreshStats);
   onRefreshStatsRef.current = onRefreshStats;
   // The realtime handler is registered once; it must reload with the current list, not the first one