fix: add missing branching files and TypeScript fix

- Add BranchRevivalCard, BranchTransitionBar, useHandoff, useResolutionOutputs, SessionQueuePage
- Fix useFlowPilotSession: add is_branching/active_branch_id defaults

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

frontend/src/hooks/useFlowPilotSession.ts

@@ -92,6 +92,8 @@ export function useFlowPilotSession(): UseFlowPilotSession {
         ticket_data: null,
         steps: [firstStep],
         conversation_messages: [],
+        is_branching: false,
+        active_branch_id: null,
       })
       setAllSteps([firstStep])
       setCurrentStep(firstStep)