Advertise an asynchronous UAC2 OUT endpoint with explicit feedback so
Windows paces USB audio from the host playback clock.
Drive feedback from measured backend consumption plus the existing
buffer phase controller. Preserve the local and backend resampler paths
for providers without active feedback.
Keep audio diagnostics in the correct clock domains, report ring and
backend latency separately, and avoid hot-path feedback wakeups.
Route audio through a provider interface. Connected transports take
priority while SPICE remains the fallback.
Carry explicit sample formats, rates, channel layouts, and source clocks
through playback and recording. Add optional presentation clock feedback
for active synchronization.
