feat: native SOCKS5 proxy support in proxy= parameter

Route SOCKS5/SOCKS5h proxies via --proxy-server Chrome arg instead of
Playwright's proxy dict (which rejects SOCKS5 with credentials).
Handles string URLs, Playwright dicts, IPv6, bypass lists.

SOCKS5 geoip exit IP resolution uses socks-proxy-agent (optional peer
dep). Falls back to DNS if not installed.

js/src/proxy.ts

@@ -23,6 +23,65 @@ export function ensureProxyScheme(proxyUrl: string): string {
  * Also handles: no credentials, URL-encoded special chars, socks5://, missing port,
  * and bare proxy strings without a scheme (e.g. "user:pass@host:port" -> treated as http).
  */
+/** Proxy dict shape accepted by Playwright/Puppeteer wrappers. */
+export type ProxyDict = { server: string; bypass?: string; username?: string; password?: string };
+
+/** Result of resolveProxyConfig — either Playwright dict OR Chrome arg, never both. */
+export interface ProxyConfig {
+  /** Playwright proxy option (for HTTP proxies). */
+  proxyOption?: ParsedProxy;
+  /** Chrome CLI args (for SOCKS5 proxies, e.g. ["--proxy-server=socks5://..."]). */
+  proxyArgs: string[];
+}
+
+/**
+ * Check if a proxy uses the SOCKS5 protocol.
+ */
+export function isSocksProxy(proxy: string | ProxyDict | undefined | null): boolean {
+  if (!proxy) return false;
+  const url = typeof proxy === "string" ? proxy : proxy.server;
+  return /^socks5h?:\/\//i.test(url);
+}
+
+/**
+ * Reconstruct a SOCKS5 URL with inline credentials from a proxy dict.
+ */
+export function reconstructSocksUrl(proxy: ProxyDict): string {
+  const url = new URL(proxy.server);
+  if (proxy.username) {
+    url.username = encodeURIComponent(proxy.username);
+    if (proxy.password) url.password = encodeURIComponent(proxy.password);
+  }
+  return url.href.replace(/\/$/, "");
+}
+
+/**
+ * Resolve proxy into Playwright option and/or Chrome args.
+ *
+ * Playwright rejects SOCKS5 proxies with credentials in its proxy dict,
+ * so SOCKS5 is passed via --proxy-server Chrome arg instead.
+ */
+export function resolveProxyConfig(proxy: string | ProxyDict | undefined): ProxyConfig {
+  if (!proxy) return { proxyArgs: [] };
+
+  if (isSocksProxy(proxy)) {
+    // SOCKS5: bypass Playwright, pass directly to Chrome via --proxy-server.
+    if (typeof proxy === "string") {
+      return { proxyArgs: [`--proxy-server=${proxy}`] };
+    }
+    const socksUrl = reconstructSocksUrl(proxy);
+    const args = [`--proxy-server=${socksUrl}`];
+    if (proxy.bypass) args.push(`--proxy-bypass-list=${proxy.bypass}`);
+    return { proxyArgs: args };
+  }
+
+  // HTTP/HTTPS: use Playwright's proxy dict
+  if (typeof proxy === "string") {
+    return { proxyOption: parseProxyUrl(proxy), proxyArgs: [] };
+  }
+  return { proxyOption: proxy as ParsedProxy, proxyArgs: [] };
+}
+
 export function parseProxyUrl(proxy: string): ParsedProxy {
   let url: URL;
   // Bare format: "user:pass@host:port" — new URL() throws without a scheme.