Allow late queue answers only after durable successful handoff

A transfer attempt can end successfully when a caller enters a hosted queue, before a human member answers. For signed answer correlation, let a durable successful handoff bypass the attempt's terminal timestamp while still requiring the inbound session and actual destination leg to be active at answer time and the match to be unique. Keep the original timestamp cutoff for unsuccessful, cancelled, and unknown outcomes: an unmoved transfer can leave a provider-confirmed leg alive, so leg lifetime alone can point to a stale attempt. This rule does not resolve shared caller ID, missing caller proof, or competing answer identities.

Applies when: a queue answer webhook arrives after an attempt-level transfer result. Keywords: Zoom LiveKit Telnyx queue answer handoff terminal timestamp stale leg correlation