Add Three.js marketing example server

New example demonstrating interactive 3D scene rendering with:
- show_threejs_scene tool with streaming code preview
- learn_threejs documentation tool
- Full WidgetProps interface for MCP App integration
- Reusable mcp-app-wrapper.tsx pattern

Also adds bun.lockb to .gitignore.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

examples/threejs-server/vite.config.ts

@@ -0,0 +1,25 @@
+import { defineConfig } from "vite";
+import react from "@vitejs/plugin-react";
+import { viteSingleFile } from "vite-plugin-singlefile";
+
+const INPUT = process.env.INPUT;
+if (!INPUT) {
+  throw new Error("INPUT environment variable is not set");
+}
+
+const isDevelopment = process.env.NODE_ENV === "development";
+
+export default defineConfig({
+  plugins: [react(), viteSingleFile()],
+  build: {
+    sourcemap: isDevelopment ? "inline" : undefined,
+    cssMinify: !isDevelopment,
+    minify: !isDevelopment,
+
+    rollupOptions: {
+      input: INPUT,
+    },
+    outDir: "dist",
+    emptyOutDir: false,
+  },
+});