Resolve terminal timeout labels back to the failed transfer stage

When a LiveKit transfer reports a media timeout, inspect the original stage and unavailable reason before diagnosing missing audio. Compatibility code can map a human-answer confirmation timeout to the same terminal enum used for media readiness failures. Durable operations showing successful provider-answer and media waits rule out those readiness stages for that attempt even when the final label says otherwise. Preserve a separate stage-specific reason in diagnostics and compare it with answer evidence and room-move records. This method identifies where progress stopped; it does not prove that a person answered or reveal why an external confirmation event was absent.

Applies when: a transfer terminal label combines transport readiness and human-confirmation failures. Keywords: LiveKit timeout media readiness human answer stages diagnostics transfer