Voicemail Status
Voice-message state carried by an MWI NOTIFY (RFC 3842). Parcelable so it can ride a single broadcast extra, mirroring RtpStreamStats.
Parsing follows RFC 3842's application/simple-message-summary body:
- the body must be that content type (other event bodies are ignored);
Messages-Waiting: yes|nois the authoritative "are there new messages" flag — it can beyeswith no per-class line at all;- the optional
Voice-Message: new/old (urgentNew/urgentOld)line refines it with counts when present.