docs: improve CI and testing documentation (#21202)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

test/manual/test_config_integration.py

@@ -4,6 +4,7 @@ Test script to verify SGLang config file integration.
 
 import argparse
 import os
+import sys
 import tempfile
 
 import pytest
@@ -162,4 +163,4 @@ def test_error_handling():
 
 
 if __name__ == "__main__":
-    pytest.main([__file__])
+    sys.exit(pytest.main([__file__]))