Coverage tool integration #596
Description
Add first-class support for running tests under coverage tools like coverage.py:
karva test --coverage
This would handle the complexity of collecting coverage across multiple parallel workers, merging .coverage files, and producing a unified report. Currently users would need to manually configure coverage run as a wrapper, which is tricky with karva's worker architecture.
Nextest integrates with cargo-llvm-cov for similar purposes:
https://nexte.st/docs/integrations/test-coverage/