fix: resolve task lane stale state, partial submit, and closure bugs

- Import and call clearTaskState before updating questions/actions in
  handleSend and handleTaskSubmit so new AI tasks always replace stale
  sessionStorage cache instead of being overridden by it
- Include pending (not yet completed) tasks in the AI message on partial
  submit so the AI knows which tasks were left unanswered
- Fix stale closure in TaskLane saveTaskLane useEffect — use refs for
  questions/actions so the debounced backend save always uses current values
- Add responses field to pending_task_lane TypeScript type, removing the
  unsafe double-cast in selectChat
- Instruct the AI to re-surface incomplete tasks unless ≥75% confident
  the information is no longer needed

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/assistant/TaskLane.tsx

@@ -130,6 +130,14 @@ export function TaskLane({ questions, actions, sessionId, onSubmit, onClose, loa
     }
   }, [handleMouseMove, handleMouseUp])
 
+  // Refs so the debounced save always uses the latest questions/actions/tasks
+  const questionsRef = useRef(questions)
+  const actionsRef = useRef(actions)
+  const tasksRef = useRef(tasks)
+  useEffect(() => { questionsRef.current = questions }, [questions])
+  useEffect(() => { actionsRef.current = actions }, [actions])
+  useEffect(() => { tasksRef.current = tasks }, [tasks])
+
   // Save task state to sessionStorage on every change + debounce to backend
   const saveTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
   useEffect(() => {
@@ -139,9 +147,9 @@ export function TaskLane({ questions, actions, sessionId, onSubmit, onClose, loa
     if (saveTimerRef.current) clearTimeout(saveTimerRef.current)
     saveTimerRef.current = setTimeout(() => {
       aiSessionsApi.saveTaskLane(sessionId, {
-        questions: questions.map(q => ({ text: q.text, context: q.context })),
-        actions: actions.map(a => ({ label: a.label, command: a.command, description: a.description })),
-        responses: tasks as unknown as Array<Record<string, unknown>>,
+        questions: questionsRef.current.map(q => ({ text: q.text, context: q.context })),
+        actions: actionsRef.current.map(a => ({ label: a.label, command: a.command, description: a.description })),
+        responses: tasksRef.current as unknown as Array<Record<string, unknown>>,
       }).catch(() => { /* silent — best-effort save */ })
     }, 2000)
     return () => { if (saveTimerRef.current) clearTimeout(saveTimerRef.current) }