ReadonlyrtpThe werift-rtp constructors the outbound RTP sender needs (loaded with the softphone).
Answers the inbound INVITE the handle parked under callId (the SIP Call-ID).
Places an OUTBOUND call (the caller-id is fixed by the registration; toNumber is the destination).
The shared SIP-registration seam this per-call SDK draws sessions from. Implemented by the process-wide import('./ringcentral-softphone-handle').RingCentralSoftphoneHandle; tests inject a fake. None of the softphone SDK's concrete types leak — only the structural SoftphoneCallSession.