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/components/session/BranchRevivalCard.tsx

@@ -0,0 +1,26 @@
+import { RotateCcw } from 'lucide-react'
+import type { BranchResponse } from '@/types/branching'
+
+interface BranchRevivalCardProps {
+  branch: BranchResponse
+  evidenceSource: BranchResponse | null
+}
+
+export function BranchRevivalCard({ branch, evidenceSource }: BranchRevivalCardProps) {
+  if (branch.status !== 'revived') return null
+
+  return (
+    <div className="bg-yellow-400/5 border border-yellow-400/20 rounded-md px-3 py-2 my-2">
+      <div className="flex items-center gap-2 text-sm">
+        <RotateCcw size={14} className="text-yellow-400" />
+        <span className="text-yellow-400 font-medium">Branch Revived</span>
+      </div>
+      {branch.evidence_description && (
+        <p className="text-xs text-secondary mt-1">{branch.evidence_description}</p>
+      )}
+      {evidenceSource && (
+        <p className="text-xs text-muted mt-0.5">Evidence from: {evidenceSource.label}</p>
+      )}
+    </div>
+  )
+}

frontend/src/components/session/BranchTransitionBar.tsx

@@ -0,0 +1,22 @@
+import { ArrowRight } from 'lucide-react'
+import type { BranchResponse } from '@/types/branching'
+
+interface BranchTransitionBarProps {
+  fromBranch: BranchResponse | null
+  toBranch: BranchResponse
+}
+
+export function BranchTransitionBar({ fromBranch, toBranch }: BranchTransitionBarProps) {
+  return (
+    <div className="bg-accent-dim border border-accent/20 rounded-md px-3 py-2 my-2 flex items-center gap-2 text-sm">
+      <span className="text-muted">Switched to</span>
+      <span className="text-accent-text font-medium">{toBranch.label}</span>
+      {fromBranch && (
+        <>
+          <ArrowRight size={12} className="text-muted" />
+          <span className="text-muted">from {fromBranch.label}</span>
+        </>
+      )}
+    </div>
+  )
+}