Versioned protocol v2

Electrical loopback.

Eligibility-led browser-local whole-path measurement with explicit limitations.

Run this protocolRead methodology
Tested with Electrical loopback v2Exact protocol, method, and runnable reference are public.<a href="/protocols/electrical-loopback-v2">Tested with Electrical loopback v2</a>

Protocol references.

Recipe reference: audio-interface-day-1-acceptance. Repeat the same signal path, preserve the protocol version with the result, and do not treat a local browser result as a hardware certification.