Merged master into feature/q0-min-coverage. Resolved conflicts in:
- benchmarks/coverage_report_bench.py: combined AST and regex benchmarks
- docs/development/testing.md: merged both versions into comprehensive guide
- robot/coverage_threshold.robot: merged test cases from both branches
- implementation_plan.md: kept both Brent and Luis notes
Fixed coverage_threshold_config test that failed because it expected
a literal --fail-under=97 but our noxfile uses the COVERAGE_THRESHOLD
constant via f-string. Updated step to resolve the constant via AST.