fix: enhance stealth mode with additional anti-detection measures

Add 7 new init scripts to cover WebGL fingerprinting, missing Chrome
APIs, permissions behavior, CDP artifacts, and HeadlessChrome UA string.
Enable Chromium's new headless mode (Channel: "chromium") when stealth
is active to use the full UI layer that is harder to detect.

Closes #58

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

browser_init.go

@@ -92,6 +92,9 @@ func initBrowser(opt BrowserOptions) (*browserInitResult, error) {
 		if len(launchArgs) > 0 {
 			launchOpts.Args = launchArgs
 		}
+		if stealth && opt.Browser == BrowserChromium && headless {
+			launchOpts.Channel = playwright.String("chromium")
+		}
 		browser, err = bt.Launch(launchOpts)
 		if err != nil {
 			return nil, fmt.Errorf("failed to launch browser: %w", err)