fix(voice-call): emit canonical session keys (#89884)
<pre style='white-space:pre-wrap;width:81ex'>fix(voice-call): emit canonical session keys (#89884) * fix(voice-call): scope generated session keys by agent * docs(voice-call): document session key canonicalization * test(voice-call): prove legacy session migration * fix(voice-call): preserve canonical session ownership * fix(sessions): isolate opaque nested identities * fix(voice-call): preserve routing ownership * fix(voice-call): enforce inbound route direction * fix(sessions): preserve migrat




