chore(examples): flip remaining Stack → Hexclave brand strings in example apps

PR 1481's sweep missed four user-visible spots in the examples/ tree:

- examples/demo: page title 'Stack Demo' + description 'using Stack...'
- examples/docs-examples: page title 'Stack Demo' + description 'using Stack...'
- examples/tanstack-start-demo: 'Stack TanStack Demo' link text in header
- examples/middleware: description 'A demo of Stack\'s middleware capabilities.'
  (title was already flipped; only the description was missed)

examples/demo/src/app/layout.tsx

@@ -7,8 +7,8 @@ import { stackServerApp } from "src/stack";
 import './global.css';
 
 export const metadata: Metadata = {
-  title: 'Stack Demo',
-  description: 'Example of using Stack as your authentication system.',
+  title: 'Hexclave Demo',
+  description: 'Example of using Hexclave as your authentication system.',
 };
 
 export default function RootLayout({

examples/docs-examples/src/app/layout.tsx

@@ -8,8 +8,8 @@ import './global.css';
 const inter = Inter({ subsets: ['latin'] });
 
 export const metadata: Metadata = {
-  title: 'Stack Demo',
-  description: 'Example of using Stack as your authentication system.',
+  title: 'Hexclave Docs Example',
+  description: 'Example of using Hexclave as your authentication system.',
 };
 
 export default function RootLayout({

examples/middleware/src/app/layout.tsx

@@ -7,7 +7,7 @@ const inter = Inter({ subsets: ["latin"] });
 
 export const metadata: Metadata = {
   title: "Hexclave Middleware Demo",
-  description: "A demo of Stack's middleware capabilities.",
+  description: "A demo of Hexclave's middleware capabilities.",
 };
 
 export default function RootLayout({

examples/tanstack-start-demo/src/components/header.tsx

@@ -8,7 +8,7 @@ export function Header() {
         <div className="mx-auto flex h-14 max-w-5xl items-center justify-between gap-4">
           <nav className="flex items-center gap-4">
             <Link to="/" className="font-semibold tracking-tight">
-              Stack TanStack Demo
+              Hexclave TanStack Demo
             </Link>
             <Link to="/ssr" className="text-sm text-zinc-600 hover:text-zinc-950 hover:transition-none dark:text-zinc-300 dark:hover:text-white">
               SSR