install.sh probed pypi.org and duckduckgo.com serially with
--max-time 8 each, so a fully blocked network cost 16s before the user
saw any useful guidance. The two probes are independent; running them
as background jobs and gathering verdicts caps the worst case at one
--max-time (8s) while the good path stays instant.
Verified live: reachable URLs 0.24s (both probes concurrent);
blackholed 10.255.255.x URLs 8.02s total (was 2x8s), warning text
unchanged. bash -n clean.
