Fixed
- SDR hardware lockups / USB contention (#256). Device probing and process shutdown now terminate decoders gently (SIGINT/SIGTERM with a SIGKILL fallback) instead of an abrupt
kill -9, so librtlsdr can release USB endpoints cleanly. The detection cache TTL was raised (fewer USB bus scans) and re-probing is skipped while a device is actively streaming. Community contribution by @Dr-gigabyte (PR #324), complementing the earlier start/stop lifecycle work.