feat: persist task lane state across reloads and session switches

TaskLane now saves user's in-progress answers (typed text, checked
items) to sessionStorage keyed by session ID. On reload or session
switch, the full task lane state restores — including partial work.

- TaskLane: saves tasks array to sessionStorage on every change,
  restores from sessionStorage on mount
- AssistantChatPage: saves task lane metadata (visibility, questions,
  actions, chatId) to sessionStorage, restores on mount
- Closing the task lane clears its sessionStorage entry

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/assistant/TaskLane.tsx

@@ -33,22 +33,51 @@ type TaskResponse = QuestionResponse | ActionResponse
 interface TaskLaneProps {
   questions: QuestionItem[]
   actions: ActionItem[]
+  sessionId?: string | null
   onSubmit: (responses: TaskResponse[]) => void
   onClose: () => void
   loading?: boolean
 }
 
+// ── Storage helpers ──
+
+const TASK_LANE_STORAGE_KEY = 'rf-tasklane-state'
+
+function saveTaskState(sessionId: string, tasks: TaskResponse[]) {
+  try {
+    sessionStorage.setItem(`${TASK_LANE_STORAGE_KEY}:${sessionId}`, JSON.stringify(tasks))
+  } catch { /* quota exceeded — ignore */ }
+}
+
+function loadTaskState(sessionId: string): TaskResponse[] | null {
+  try {
+    const stored = sessionStorage.getItem(`${TASK_LANE_STORAGE_KEY}:${sessionId}`)
+    return stored ? JSON.parse(stored) : null
+  } catch { return null }
+}
+
+export function clearTaskState(sessionId: string) {
+  try { sessionStorage.removeItem(`${TASK_LANE_STORAGE_KEY}:${sessionId}`) } catch { /* ignore */ }
+}
+
 // ── Component ──
 
-export function TaskLane({ questions, actions, onSubmit, onClose, loading }: TaskLaneProps) {
-  const [tasks, setTasks] = useState<TaskResponse[]>(() => [
-    ...questions.map((q): QuestionResponse => ({
-      type: 'question', text: q.text, context: q.context, state: 'pending', value: '',
-    })),
-    ...actions.map((a): ActionResponse => ({
-      type: 'action', label: a.label, command: a.command, description: a.description, state: 'pending', value: '',
-    })),
-  ])
+export function TaskLane({ questions, actions, sessionId, onSubmit, onClose, loading }: TaskLaneProps) {
+  const [tasks, setTasks] = useState<TaskResponse[]>(() => {
+    // Try to restore saved state for this session (preserves user's in-progress answers)
+    if (sessionId) {
+      const saved = loadTaskState(sessionId)
+      if (saved && saved.length > 0) return saved
+    }
+    return [
+      ...questions.map((q): QuestionResponse => ({
+        type: 'question', text: q.text, context: q.context, state: 'pending', value: '',
+      })),
+      ...actions.map((a): ActionResponse => ({
+        type: 'action', label: a.label, command: a.command, description: a.description, state: 'pending', value: '',
+      })),
+    ]
+  })
   const [submitting, setSubmitting] = useState(false)
   const [showRunAll, setShowRunAll] = useState(false)
   const [showPreview, setShowPreview] = useState(false)
@@ -100,6 +129,11 @@ export function TaskLane({ questions, actions, onSubmit, onClose, loading }: Tas
     }
   }, [handleMouseMove, handleMouseUp])
 
+  // Save task state to sessionStorage on every change
+  useEffect(() => {
+    if (sessionId) saveTaskState(sessionId, tasks)
+  }, [sessionId, tasks])
+
   // Reset when new tasks come in from AI response
   useEffect(() => {
     // eslint-disable-next-line react-hooks/set-state-in-effect -- intentional: syncs derived state from prop changes