Fix sidebar session list responsiveness

frontend/app/components/assistant-ui/threadlist-sidebar.tsx

@@ -117,7 +117,7 @@ export function ThreadListSidebar({
 						<SidebarTrigger className="size-8 shrink-0" />
 					</div>
 				</SidebarHeader>
-				<SidebarContent className="aui-sidebar-content px-2">
+				<SidebarContent className="aui-sidebar-content overflow-hidden px-2">
 					<ThreadList />
 				</SidebarContent>
 				<SidebarRail />
@@ -341,7 +341,7 @@ function useSidebarSessions(open: boolean) {
 			.then((res) => (res.ok ? res.json() : []))
 			.then((payload) => {
 				if (cancelled || !Array.isArray(payload)) return;
-				setSessions(dedupeSidebarSessions(payload).slice(0, 12));
+				setSessions(dedupeSidebarSessions(payload));
 			})
 			.catch(() => {
 				if (!cancelled) setSessions([]);