Add Comprehensive Library API Tests

[heysamtexas]

Summary

Create comprehensive test suite for the new library API to ensure reliability for external consumers.

Acceptance Criteria

• Create test suite for GitHubAnalyzer class
• Test AnalysisConfig builder pattern and validation
• Test AnalysisResult object properties and methods
• Test progress callback functionality
• Test both sync and async API variants
• Test error handling and custom exceptions
• Achieve >95% coverage for library API surface
• Performance tests to ensure no regression

Files to Create/Modify

• tests/test_library_api.py (new)
• tests/test_analysis_config.py (new)
• tests/test_progress_callbacks.py (new)
• Update existing tests as needed

Dependencies

• All implementation issues (Create Progress Callback System with ProgressEvent Types #35-42) must be complete

Definition of Done

• Comprehensive test coverage for library API
• All tests pass consistently
• Performance benchmarks show no regression
• Library reliability is validated for external use