feat: add 3 new tutorials (first-tool, agent-example, playground)

- Build Your First Tool: Step-by-step guide from npm init to published
- Real-World Agent: Complete working example with meta-tools
- Interactive Playground: How to test tools in browser

Each tutorial has 5-6 slides with code examples and animations.
Updated main page to show all 6 tutorials in grid.

apps/tutorial/src/app/first-tool/page.tsx

@@ -0,0 +1,16 @@
+import { FirstToolSlideshow } from '@/components/FirstToolSlideshow';
+import type { Metadata } from 'next';
+
+export const metadata: Metadata = {
+  title: 'Build Your First Tool | TPMJS Tutorials',
+  description:
+    'Step-by-step guide to creating your first AI SDK tool for the TPMJS registry. From npm init to published tool in 10 minutes.',
+};
+
+export default function FirstToolPage(): React.ReactElement {
+  return (
+    <main className="h-screen w-screen overflow-hidden">
+      <FirstToolSlideshow />
+    </main>
+  );
+}