Add regression tests for PR RLabs-Inc#9 fixes, format and lint code

Tests added:
- test_cli_response_extraction: Validates nested Claude Code message format handling (message.message.content)
- test_json_parsing_fallback: Validates ast.literal_eval fallback for single-quote JSON from LLM
- test_storage_stats: Validates get_stats() returns real database counts

Code changes:
- Formatted all source files with black
- Fixed ruff linting issues (unused imports, import ordering, trailing whitespace)
- Removed f-string prefix from strings without placeholders
- Removed unused variable assignments

All tests verified to fail on main branch and pass on this branch.

Author: jespo2021