refactor: remove dead stealth args, let binary handle GPU diversity

Remove --disable-blink-features=AutomationControlled (dead, binary handles
navigator.webdriver at source level) and hardcoded GPU vendor/renderer flags.
Binary auto-generates diverse GPU profiles from fingerprint seed. Improves
fingerprint diversity -- previously every user shared the same GPU string.

Bump to v0.3.21.

tests/test_config.py

@@ -133,10 +133,14 @@ class TestStealthArgs:
         with patch("cloakbrowser.config.platform.system", return_value="Darwin"):
             args = get_default_stealth_args()
             assert "--fingerprint-platform=macos" in args
-            assert any("Apple" in a for a in args)
+            # GPU flags removed — binary auto-generates from seed + platform
+            assert not any("fingerprint-gpu-vendor" in a for a in args)
+            assert not any("fingerprint-gpu-renderer" in a for a in args)
 
     def test_linux_windows_profile(self):
         with patch("cloakbrowser.config.platform.system", return_value="Linux"):
             args = get_default_stealth_args()
             assert "--fingerprint-platform=windows" in args
-            assert any("NVIDIA" in a for a in args)
+            # GPU flags removed — binary auto-generates from seed + platform
+            assert not any("fingerprint-gpu-vendor" in a for a in args)
+            assert not any("fingerprint-gpu-renderer" in a for a in args)