Output now mirrors sunbeam status (namespace headers, checks indented
below). Any uncaught exception from a check is caught in cmd_check
and displayed as a failed check instead of crashing.
Also fix _http_get: TimeoutError and other raw OSError/SSL errors that
Python 3.13 doesn't always wrap in URLError are now normalized to
URLError before re-raising, so each check function's URLError handler
reliably catches all network failures.