feat(webui): add temporary chat mode

webui/src/components/Sidebar.tsx

@@ -8,6 +8,7 @@ import {
   Archive,
   Brain,
   CalendarClock,
+  MessageCircleDashed,
   Menu,
   Search,
   Settings,
@@ -34,7 +35,9 @@ interface SidebarProps {
   activeKey: string | null;
   loading: boolean;
   newChatActive: boolean;
+  temporaryChatActive: boolean;
   onNewChat: () => void;
+  onOpenTemporaryChat: () => void;
   onSelect: (key: string) => void;
   onRequestDelete: (key: string, label: string) => void;
   onTogglePin: (key: string) => void;
@@ -95,8 +98,10 @@ export function Sidebar(props: SidebarProps) {
   const toggleLabel = t("thread.header.toggleSidebar");
   const newChatShortcut = newChatShortcutLabel();
   const activeActionRef = useRef<HTMLButtonElement>(null);
-  const activeActionId = props.newChatActive
-    ? "new-chat"
+  const activeActionId = props.temporaryChatActive
+    ? "temporary-chat"
+    : props.newChatActive
+      ? "new-chat"
     : props.activeUtility
       ? `utility:${props.activeUtility}`
       : null;
@@ -170,6 +175,14 @@ export function Sidebar(props: SidebarProps) {
           shortcut={newChatShortcut}
           ariaKeyShortcuts="Meta+Shift+O Control+Shift+O"
         />
+        <SidebarActionButton
+          collapsed={collapsed}
+          label={t("temporaryChat.title")}
+          onClick={props.onOpenTemporaryChat}
+          active={props.temporaryChatActive}
+          selectionRef={activeActionRef}
+          icon={<MessageCircleDashed className="h-4 w-4" />}
+        />
         <SidebarActionButton
           collapsed={collapsed}
           label={t("sidebar.searchAria")}