Add example-tool-loop binary wrapper for npx usage

Created a wrapper script that properly launches the backfill proxy
with the tool loop server, making it easy to run via npx.

The bin entry now points to dist/esm/bin/examples-tool-loop.js which
spawns the backfill proxy with the server as a child process.

Usage:
  npx -y --package=https://github.com/modelcontextprotocol/typescript-sdk.git#ochafik/sep1577 -- example-tool-loop

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

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

Author: ochafik

package.json

@@ -20,7 +20,7 @@
   ],
   "bin": {
     "backfill-sampling": "./dist/esm/examples/backfill/backfillSampling.js",
-    "example-tool-loop": "./dist/esm/examples/server/toolLoopSampling.js"
+    "example-tool-loop": "./dist/esm/bin/examples-tool-loop.js"
   },
   "exports": {
     ".": {

src/bin/examples-tool-loop.ts

@@ -0,0 +1,22 @@
+#!/usr/bin/env node
+
+import { spawn } from 'node:child_process';
+import { fileURLToPath } from 'node:url';
+import { dirname, join } from 'node:path';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+// Navigate from dist/esm/bin/ to dist/esm/examples/
+const backfillScript = join(__dirname, '../examples/backfill/backfillSampling.js');
+const serverScript = join(__dirname, '../examples/server/toolLoopSampling.js');
+
+// Run the backfill proxy with the tool loop server
+const child = spawn('node', [backfillScript, 'node', serverScript], {
+  stdio: 'inherit',
+  env: process.env
+});
+
+child.on('exit', (code) => {
+  process.exit(code || 0);
+});