Adds extensive test coverage for ListOutputConverter and StreamHelper to improve robustness and handle edge cases.

Changes Made

ListOutputConverter Tests

• CSV format variations (spacing, empty values, special characters)
• Edge cases (trailing commas, whitespace handling, alternative delimiters)
• Data type preservation and boundary conditions
• Parameterized testing for multiple input patterns

StreamHelper Tests

• Error event processing with different error types
• Multiple sequential error handling
• Content block reference state management

Improvements

• Better edge case coverage for CSV parsing
• Improved error handling validation for streaming
• Enhanced reliability for real-world scenarios
• Maintains existing test patterns and conventions