The test file expects compute_file_complexity(), calculate_refactoring_score(),
and FileMetrics from the script, but only a stub generate_proposals() existed.
Implemented:
- compute_file_complexity(): AST-based cyclomatic complexity analysis
- calculate_refactoring_score(): weighted scoring (complexity, size, churn, coverage)
- FileMetrics: dataclass with all required fields
- Full generate_proposals() that scans directories and produces scored proposals
All 10 tests pass. py_compile succeeds.
Closes#210