Re-runs of --vs-unbound-cold were hitting stale cache entries from
prior runs. The static COUNTER reset to 0 each process, generating
the same c0.example.com subdomains. With the 1-hour stale window,
entries from 10 minutes ago served as stale hits.
Fix: prefix with PID (r{pid}-c{n}.domain) and flush Numa's cache
before cold benchmarks.