Add ASV benchmark modules to track test suite performance over time:
- bench_unit_tests.py: Feature discovery, step module loading, parallel
chunk computation, behave config parsing, and test suite metrics
- bench_coverage_report.py: Coverage collection pipeline timing and
report generation overhead
- bench_subprocess_overhead.py: Subprocess count tracking and per-feature
startup cost measurement
These benchmarks establish baselines for the post-optimization state
and enable CI-driven regression detection.
ISSUES CLOSED: #486
freemo