feat: AI marker system prompt fixes, TaskLane activation, and FlowPilot updates

- Fix system prompt to ensure [QUESTIONS]/[ACTIONS] markers in AI responses
- Add format reminder injection to user messages for marker compliance
- Wire TaskLane activation in prefill and resume paths
- Add ActionCardGroup component for structured question/action rendering
- Update FlowPilot session and step card components
- Update ai-session schemas and types for marker data

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

frontend/src/components/flowpilot/FlowPilotSession.tsx

@@ -10,6 +10,7 @@ import type {
   StatusUpdateContext,
   StatusUpdateResponse,
 } from '@/types/ai-session'
+import type { BranchResponse } from '@/types/branching'
 import { ConfidenceIndicator } from './ConfidenceIndicator'
 import { FlowPilotStepCard } from './FlowPilotStepCard'
 import { FlowPilotMessageBar } from './FlowPilotMessageBar'
@@ -17,6 +18,8 @@ import { SessionDocView } from './SessionDocView'
 import { StatusUpdateModal } from './StatusUpdateModal'
 import { SessionTicketCard } from './SessionTicketCard'
 import { SimilarSessions } from './SimilarSessions'
+import { BranchMap } from '@/components/session/BranchMap'
+import { BranchTransitionBar } from '@/components/session/BranchTransitionBar'
 import { TicketPickerModal } from '@/components/session/TicketPickerModal'
 import { aiSessionsApi } from '@/api'
 import { toast } from '@/lib/toast'
@@ -36,6 +39,10 @@ interface FlowPilotSessionProps {
   onRate: (rating: number) => void
   onReloadSession?: () => Promise<void>
   onGenerateStatusUpdate?: (audience: StatusUpdateAudience, length: StatusUpdateLength, context: StatusUpdateContext) => Promise<StatusUpdateResponse>
+  // Branching props (optional — only present for branching sessions)
+  branches?: BranchResponse[]
+  activeBranchId?: string | null
+  onBranchSwitch?: (branchId: string) => void
 }
 
 export function FlowPilotSession({
@@ -52,12 +59,34 @@ export function FlowPilotSession({
   onRate,
   onReloadSession,
   onGenerateStatusUpdate,
+  branches,
+  activeBranchId,
+  onBranchSwitch,
 }: FlowPilotSessionProps) {
   const scrollRef = useRef<HTMLDivElement>(null)
   const [showTicketPicker, setShowTicketPicker] = useState(false)
   const [linkingTicket, setLinkingTicket] = useState(false)
   const [showShareCommunication, setShowShareCommunication] = useState(false)
   const [showMobileSidebar, setShowMobileSidebar] = useState(false)
+  const prevBranchIdRef = useRef<string | null>(null)
+  const [branchTransition, setBranchTransition] = useState<{
+    from: BranchResponse | null
+    to: BranchResponse
+  } | null>(null)
+
+  // Track branch switches and show transition bar
+  useEffect(() => {
+    if (!activeBranchId || !branches?.length) return
+    const prev = prevBranchIdRef.current
+    if (prev && prev !== activeBranchId) {
+      const fromBranch = branches.find(b => b.id === prev) ?? null
+      const toBranch = branches.find(b => b.id === activeBranchId)
+      if (toBranch) {
+        setBranchTransition({ from: fromBranch, to: toBranch })
+      }
+    }
+    prevBranchIdRef.current = activeBranchId
+  }, [activeBranchId, branches])
 
   const handleLinkTicket = async (ticketId: string, _ticket: PSATicketInfo) => {
     if (!session.psa_connection_id && !session.ticket_data) {
@@ -218,6 +247,14 @@ export function FlowPilotSession({
         {/* Conversation column — pb-24 provides clearance for the fixed message bar */}
         <div ref={scrollRef} className="flex-1 overflow-y-auto p-3 pb-24 sm:p-4 sm:pb-24 lg:p-6 lg:pb-24">
           <div className="mx-auto max-w-2xl space-y-3">
+            {/* Branch transition bar */}
+            {branchTransition && (
+              <BranchTransitionBar
+                fromBranch={branchTransition.from}
+                toBranch={branchTransition.to}
+              />
+            )}
+
             {allSteps.map((step) => (
               <FlowPilotStepCard
                 key={step.step_id}
@@ -226,6 +263,8 @@ export function FlowPilotSession({
                 isProcessing={isProcessing && currentStep?.step_id === step.step_id}
                 sessionId={session.id}
                 onRespond={onRespond}
+                onBranchSwitch={onBranchSwitch}
+                activeBranchId={activeBranchId}
               />
             ))}
           </div>
@@ -236,6 +275,15 @@ export function FlowPilotSession({
           className="hidden w-72 shrink-0 overflow-y-auto border-l border-border p-4 lg:block"
         >
           <div className="space-y-4">
+            {/* Branch map (branching sessions only) */}
+            {session.is_branching && branches && branches.length > 0 && onBranchSwitch && (
+              <BranchMap
+                branches={branches}
+                activeBranchId={activeBranchId ?? null}
+                onSelectBranch={onBranchSwitch}
+              />
+            )}
+
             {/* Ticket context */}
             {session.psa_ticket_id ? (
               <SessionTicketCard