docs: add MCP client configuration to example READMEs

Add stdio transport configuration snippets near the top of each example
README to help users quickly set up the servers in their MCP clients.

- Node.js examples use npx with the published npm packages
- Python qr-server uses uv with local path
- Removed Claude Desktop-specific references from qr-server

examples/basic-server-react/README.md

@@ -7,6 +7,27 @@ An MCP App example with a React UI.
 > [!TIP]
 > Looking for a vanilla JavaScript example? See [`basic-server-vanillajs`](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-server-vanillajs)!
 
+## MCP Client Configuration
+
+Add to your MCP client configuration (stdio transport):
+
+```json
+{
+  "mcpServers": {
+    "basic-react": {
+      "command": "npx",
+      "args": [
+        "-y",
+        "--silent",
+        "--registry=https://registry.npmjs.org/",
+        "@modelcontextprotocol/server-basic-react",
+        "--stdio"
+      ]
+    }
+  }
+}
+```
+
 ## Overview
 
 - Tool registration with a linked UI resource