wip(handoff): start issue cleanup plan sections 1 and 2

Co-Authored-By: Codex <noreply@openai.com>

frontend/src/pages/SessionHistoryPage.tsx

@@ -269,7 +269,7 @@ export default function SessionHistoryPage() {
       <PageMeta title="Sessions" />
       <div className="container mx-auto px-4 py-6 sm:px-6 sm:py-8">
         {/* Page heading */}
-        <div className="mb-6">
+        <div className="mb-6" data-testid="session-history-heading">
           <h1 className="text-2xl font-heading font-bold text-foreground sm:text-3xl">Session History</h1>
           <p className="mt-1 text-sm text-muted-foreground">View and manage your sessions</p>
         </div>
@@ -279,6 +279,7 @@ export default function SessionHistoryPage() {
           {TABS.map((tab) => (
             <button
               key={tab.id}
+              data-testid={`session-history-tab-${tab.id}`}
               onClick={() => setActiveTab(tab.id)}
               className={cn(
                 'px-4 py-2 text-sm transition-colors whitespace-nowrap',
@@ -614,6 +615,7 @@ export default function SessionHistoryPage() {
                                   Close
                                 </button>
                                 <button
+                                  data-testid="flow-session-resume"
                                   onClick={() => navigate(getSessionResumePath(session.tree_id, session.tree_snapshot?.tree_type), { state: { sessionId: session.id } })}
                                   className="rounded-md bg-primary px-3 py-2 text-sm font-medium text-white hover:brightness-110 transition-all"
                                 >