tests/cli(test[search]): Add comprehensive unit test coverage

why: New search module needed unit tests for helper functions and edge cases.
what:
- Add unit tests for normalize_fields, parse_query_terms, compile_search_patterns
- Add highlight_text tests with color modes enabled/disabled
- Add search_repos tests for url/workspace field matches, error handling
- Test auto-discover config path and invalid input handling

Author: tony