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/pages/FlowPilotSessionPage.tsx

@@ -2,9 +2,12 @@ import { useEffect, useRef, useState } from 'react'
 import { useParams, useSearchParams, useLocation, useBlocker, useNavigate } from 'react-router-dom'
 import { Sparkles, Loader2, AlertTriangle, CheckCircle2, ArrowUpRight, FileText, MoreHorizontal, Pause, X } from 'lucide-react'
 import { useFlowPilotSession } from '@/hooks/useFlowPilotSession'
+import { useBranching } from '@/hooks/useBranching'
 import { FlowPilotIntake, FlowPilotSession, SessionBriefing } from '@/components/flowpilot'
 import { EscalateModal } from '@/components/flowpilot/EscalateModal'
 import { StatusUpdateModal } from '@/components/flowpilot/StatusUpdateModal'
+import { HandoffModal } from '@/components/session/HandoffModal'
+import { handoffsApi } from '@/api/handoffs'
 import { aiSessionsApi } from '@/api'
 import { toast } from '@/lib/toast'
 
@@ -16,12 +19,14 @@ export default function FlowPilotSessionPage() {
   const prefill = (location.state as { prefill?: string } | null)?.prefill || ''
   const isPickup = searchParams.get('pickup') === 'true'
   const fp = useFlowPilotSession()
+  const branching = useBranching()
   const prefillHandledRef = useRef(false)
   const [showOverflow, setShowOverflow] = useState(false)
   const [showResolve, setShowResolve] = useState(false)
   const [showEscalate, setShowEscalate] = useState(false)
   const [showAbandon, setShowAbandon] = useState(false)
   const [showStatusUpdate, setShowStatusUpdate] = useState(false)
+  const [showHandoff, setShowHandoff] = useState(false)
   const [resolutionSummary, setResolutionSummary] = useState('')
   const [submitting, setSubmitting] = useState(false)
 
@@ -48,6 +53,13 @@ export default function FlowPilotSessionPage() {
     }
   }, [sessionId]) // eslint-disable-line react-hooks/exhaustive-deps
 
+  // Load branches when session is branching
+  useEffect(() => {
+    if (fp.session?.is_branching && fp.session.id) {
+      branching.loadBranches(fp.session.id)
+    }
+  }, [fp.session?.is_branching, fp.session?.id]) // eslint-disable-line react-hooks/exhaustive-deps
+
   const handlePickupContinue = async () => {
     if (!sessionId) return
     setPickingUp(true)
@@ -64,6 +76,15 @@ export default function FlowPilotSessionPage() {
     }
   }
 
+  const handleBranchSwitch = async (branchId: string) => {
+    if (!fp.session) return
+    const result = await branching.switchBranch(fp.session.id, branchId)
+    if (result) {
+      // Reload session to get updated steps for the switched branch
+      await fp.loadSession(fp.session.id)
+    }
+  }
+
   const handlePickupFresh = async (context: string) => {
     if (!sessionId) return
     setPickingUp(true)
@@ -375,6 +396,9 @@ export default function FlowPilotSessionPage() {
           onRate={fp.rateSession}
           onReloadSession={() => fp.loadSession(fp.session!.id)}
           onGenerateStatusUpdate={(audience, length, context) => fp.generateStatusUpdate({ audience, length, context })}
+          branches={branching.branches}
+          activeBranchId={branching.activeBranchId}
+          onBranchSwitch={handleBranchSwitch}
         />
       </div>
 
@@ -476,6 +500,18 @@ export default function FlowPilotSessionPage() {
         context="status"
         hasPsaTicket={!!fp.session.psa_ticket_id}
       />
+
+      {/* Handoff modal (branching sessions) */}
+      {fp.session.is_branching && showHandoff && (
+        <HandoffModal
+          onClose={() => setShowHandoff(false)}
+          onSubmit={async (data) => {
+            await handoffsApi.createHandoff(fp.session!.id, data)
+            setShowHandoff(false)
+            toast.success('Handoff created')
+          }}
+        />
+      )}
     </div>
   )
 }