Release and Packaging: Clean up (#3489)

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+# Example Proxy Script
+
+The following is an example of a proxy script that can be used with the `GEMINI_SANDBOX_PROXY_COMMAND` environment variable. This script only allows `HTTPS` connections to `example.com:443` and declines all other requests.
+
+```javascript
+#!/usr/bin/env node
+
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+// Example proxy server that listens on :::8877 and only allows HTTPS connections to example.com.
+// Set `GEMINI_SANDBOX_PROXY_COMMAND=scripts/example-proxy.js` to run proxy alongside sandbox
+// Test via `curl https://example.com` inside sandbox (in shell mode or via shell tool)
+
+import http from 'http';
+import net from 'net';
+import { URL } from 'url';
+import console from 'console';
+
+const PROXY_PORT = 8877;
+const ALLOWED_DOMAINS = ['example.com', 'googleapis.com'];
+const ALLOWED_PORT = '443';
+
+const server = http.createServer((req, res) => {
+  // Deny all requests other than CONNECT for HTTPS
+  console.log(
+    `[PROXY] Denying non-CONNECT request for: ${req.method} ${req.url}`,
+  );
+  res.writeHead(405, { 'Content-Type': 'text/plain' });
+  res.end('Method Not Allowed');
+});
+
+server.on('connect', (req, clientSocket, head) => {
+  // req.url will be in the format "hostname:port" for a CONNECT request.
+  const { port, hostname } = new URL(`http://${req.url}`);
+
+  console.log(`[PROXY] Intercepted CONNECT request for: ${hostname}:${port}`);
+
+  if (
+    ALLOWED_DOMAINS.some(
+      (domain) => hostname == domain || hostname.endsWith(`.${domain}`),
+    ) &&
+    port === ALLOWED_PORT
+  ) {
+    console.log(`[PROXY] Allowing connection to ${hostname}:${port}`);
+
+    // Establish a TCP connection to the original destination.
+    const serverSocket = net.connect(port, hostname, () => {
+      clientSocket.write('HTTP/1.1 200 Connection Established\r\n\r\n');
+      // Create a tunnel by piping data between the client and the destination server.
+      serverSocket.write(head);
+      serverSocket.pipe(clientSocket);
+      clientSocket.pipe(serverSocket);
+    });
+
+    serverSocket.on('error', (err) => {
+      console.error(`[PROXY] Error connecting to destination: ${err.message}`);
+      clientSocket.end(`HTTP/1.1 502 Bad Gateway\r\n\r\n`);
+    });
+  } else {
+    console.log(`[PROXY] Denying connection to ${hostname}:${port}`);
+    clientSocket.end('HTTP/1.1 403 Forbidden\r\n\r\n');
+  }
+
+  clientSocket.on('error', (err) => {
+    // This can happen if the client hangs up.
+    console.error(`[PROXY] Client socket error: ${err.message}`);
+  });
+});
+
+server.listen(PROXY_PORT, () => {
+  const address = server.address();
+  console.log(`[PROXY] Proxy listening on ${address.address}:${address.port}`);
+  console.log(
+    `[PROXY] Allowing HTTPS connections to domains: ${ALLOWED_DOMAINS.join(', ')}`,
+  );
+});
+```