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/pages/AssistantChatPage.tsx

@@ -12,7 +12,7 @@ import { analytics } from '@/lib/analytics'
 import { toast } from '@/lib/toast'
 import { ChatSidebar, ChatSidebarCollapsedBar } from '@/components/assistant/ChatSidebar'
 import { ChatMessage } from '@/components/assistant/ChatMessage'
-import { TaskLane } from '@/components/assistant/TaskLane'
+import { TaskLane, clearTaskState } from '@/components/assistant/TaskLane'
 import { ConcludeSessionModal } from '@/components/assistant/ConcludeSessionModal'
 import { StatusUpdateModal } from '@/components/flowpilot/StatusUpdateModal'
 import type { ChatListItem, ConclusionOutcome } from '@/types/assistant-chat'
@@ -242,7 +242,7 @@ export default function AssistantChatPage() {
         if (q.length > 0 || a.length > 0) {
           // Pre-load user's saved responses into sessionStorage BEFORE setting props
           // so TaskLane can restore them on mount/prop-change
-          const responses = (detail.pending_task_lane as Record<string, unknown>).responses as unknown[] | undefined
+          const responses = detail.pending_task_lane.responses
           if (responses && responses.length > 0) {
             try {
               sessionStorage.setItem(`rf-tasklane-state:${chatId}`, JSON.stringify(responses))
@@ -340,6 +340,7 @@ export default function AssistantChatPage() {
       const hasQuestions = response.questions && response.questions.length > 0
       const hasActions = response.actions && response.actions.length > 0
       if (hasQuestions || hasActions) {
+        if (activeChatId) clearTaskState(activeChatId)
         setActiveQuestions(response.questions || [])
         setActiveActions(response.actions || [])
         setShowTaskLane(true)
@@ -358,7 +359,8 @@ export default function AssistantChatPage() {
   const handleTaskSubmit = async (responses: Array<{ type: string; state: string; value: string; text?: string; label?: string }>) => {
     if (!activeChatId || loading) return
 
-    // Format task responses into a structured message for the AI
+    // Format task responses into a structured message for the AI.
+    // Pending tasks are included so the AI knows they weren't completed yet.
     const parts: string[] = []
     for (const r of responses) {
       const name = r.type === 'question' ? `Q: ${r.text}` : r.label || 'Check'
@@ -366,6 +368,8 @@ export default function AssistantChatPage() {
         parts.push(`**${name}:**\n\`\`\`\n${r.value.trim()}\n\`\`\``)
       } else if (r.state === 'skipped') {
         parts.push(`**${name}:** _(skipped)_`)
+      } else {
+        parts.push(`**${name}:** _(not yet completed)_`)
       }
     }
     const userMessage = parts.join('\n\n')
@@ -385,6 +389,7 @@ export default function AssistantChatPage() {
       // Update task lane based on AI response
       const hasQuestions = response.questions && response.questions.length > 0
       const hasActions = response.actions && response.actions.length > 0
+      if (activeChatId) clearTaskState(activeChatId)
       if (hasQuestions || hasActions) {
         setActiveQuestions(response.questions || [])
         setActiveActions(response.actions || [])