Count one underrun per starvation episode and end the sync diagnostics
epoch when a logical source stops.
Resume a compatible backend synchronously so data after a same-wire
restart is accepted immediately. Rebase the first post-idle device tick
without passing a long gap through the short-step clock filter.
Cancel in-flight backlog trims before fresh audio can be queued.
Recover stable local playback in the device clock domain and restart
rate control from the measured feed-forward clock ratio.
Ignore catch-up packet sizing until the normal source cadence returns.
Do not learn late delivery from packets that already caused an
underrun and media-clock rebase. Preserve learned jitter only across
continuous playback.
