* test: run the suite under pytest-xdist and fix the isolation bugs that exposed (#171)
* test: address review — cgroup+affinity-aware worker count, dedupe cuda_available, close remaining isolation leaks (#171)
* test: fix cpu_topology cross-platform breakage, cover the fallback branches, correct CONTRIBUTING (#171)
* test: -n auto no longer returns a single worker on one physical core (#171)