fix(webui): show platform-specific new chat shortcut

webui/src/components/Sidebar.tsx

@@ -55,12 +55,29 @@ interface SidebarProps {
   hostChromeInset?: boolean;
 }
 
+type NavigatorWithUserAgentData = Navigator & {
+  userAgentData?: { platform?: string };
+};
+
+function isApplePlatform(): boolean {
+  if (typeof navigator === "undefined") return false;
+  const platform = navigator.platform || "";
+  const userAgentPlatform =
+    (navigator as NavigatorWithUserAgentData).userAgentData?.platform || "";
+  return /mac|iphone|ipad|ipod/i.test(`${platform} ${userAgentPlatform}`);
+}
+
+function newChatShortcutLabel(): string {
+  return isApplePlatform() ? "⌘⇧O" : "Ctrl+Shift+O";
+}
+
 export function Sidebar(props: SidebarProps) {
   const { t } = useTranslation();
   const [menuPortalContainer, setMenuPortalContainer] =
     useState<HTMLElement | null>(null);
   const collapsed = Boolean(props.collapsed);
   const toggleLabel = t("thread.header.toggleSidebar");
+  const newChatShortcut = newChatShortcutLabel();
 
   return (
     <nav
@@ -124,7 +141,8 @@ export function Sidebar(props: SidebarProps) {
           label={t("sidebar.newChat")}
           onClick={props.onNewChat}
           icon={<SquarePen className="h-4 w-4" />}
-          shortcut="Cmd/Ctrl+Shift+O"
+          shortcut={newChatShortcut}
+          ariaKeyShortcuts="Meta+Shift+O Control+Shift+O"
         />
         <SidebarActionButton
           collapsed={collapsed}
@@ -215,6 +233,7 @@ function SidebarActionButton({
   active = false,
   className,
   shortcut,
+  ariaKeyShortcuts,
 }: {
   collapsed: boolean;
   label: string;
@@ -223,6 +242,7 @@ function SidebarActionButton({
   active?: boolean;
   className?: string;
   shortcut?: string;
+  ariaKeyShortcuts?: string;
 }) {
   const title = shortcut ? `${label} (${shortcut})` : collapsed ? label : undefined;
 
@@ -232,6 +252,7 @@ function SidebarActionButton({
       variant="ghost"
       aria-label={label}
       aria-current={active ? "page" : undefined}
+      aria-keyshortcuts={ariaKeyShortcuts}
       title={title}
       onClick={() => onClick()}
       className={cn(