fix(desperado): report live SDR stream termination

[xoolive]

Summary

• surface unexpected live-stream termination through Error::StreamTerminated instead of silently ending the async source;
• preserve fatal USB endpoint and repeated-transfer errors in RTL-SDR, Airspy, and HackRF multi-transfer readers;
• treat zero-length and read-error SoapySDR exits as terminal stream errors;
• update RTL-SDR, Airspy, and HackRF examples to exercise result-bearing multi-transfer readers.

Validation

• cargo test -p desperado --all-features
• cargo test -p rs-rtl -p rs-spy -p rs-hackrf
• cargo check -p desperado --all-features --examples
• manually unplugged RTL-SDR, Airspy, and HackRF devices; each reported a terminal stream error.