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/pdf-server/README.md

@@ -4,6 +4,27 @@
 
 A simple interactive PDF viewer that uses [PDF.js](https://mozilla.github.io/pdf.js/). Launch it w/ a few PDF files and/or URLs as CLI args (+ support loading any additional pdf from arxiv.org).
 
+## MCP Client Configuration
+
+Add to your MCP client configuration (stdio transport):
+
+```json
+{
+  "mcpServers": {
+    "pdf": {
+      "command": "npx",
+      "args": [
+        "-y",
+        "--silent",
+        "--registry=https://registry.npmjs.org/",
+        "@modelcontextprotocol/server-pdf",
+        "--stdio"
+      ]
+    }
+  }
+}
+```
+
 ## What This Example Demonstrates
 
 ### 1. Chunked Data Through Size-Limited Tool Calls