Feature request: Visual Voicemail service (list, transcripts, and audio for carrier and FaceTime voicemails)

[bradhallett]

Is your feature request related to a problem? Please describe.

macOS 26 ships a Phone app that syncs iPhone voicemail to the Mac. iMCP's Phone service exposes call history, but MCP clients currently have no way to see voicemails: who left them, when, their transcripts, or the audio itself. Anything voicemail-related still requires picking up the phone.

Describe the solution you'd like

A new Voicemail service with three read-only tools:

• voicemails_fetch — list voicemail messages: sender, date, duration, read/unread, type (carrier voicemail / FaceTime audio message / FaceTime video message), and whether a transcript exists
• voicemail_transcript_fetch — the transcript of one message: flattened text plus per-segment text and confidence
• voicemail_audio_fetch — the audio of one message (audio/amr for carrier voicemail, audio/mp4 for FaceTime audio messages)

Where the data lives (verified on a live Mac with a populated store)

On macOS 26+, the facetimemessagestored daemon mirrors carrier and FaceTime voicemails into a CoreData store at

~/Library/Group Containers/group.com.apple.FaceTime/com.apple.facetimemessagestored/Data Store/FaceTimeMessageStore-local.sqlitedb

• Voicemails are rows of the ZSTOREDMESSAGE table: ZFROM (sender), ZDATECREATED, ZDURATION, ZISREAD, ZMESSAGETYPE, ZMAILBOXTYPE, ZTRANSCRIPTIONSTATUS, ZDATEDELETED, and friends.
• Transcripts are inline ZTRANSCRIPT blobs: NSKeyedArchiver-encoded binary plists holding either a VMVoicemailTranscript (transcriptionString, confidence, confidenceRating, segments) or an array of segment dictionaries (text, confidence).
• Audio assets live in an Assets tree beside the database: Assets/<first two hex digits>/<UUID>.amr (carrier voicemail, GSM AMR), .../<UUID>.m4a (FaceTime audio message), and .../<UUID>.MOV (FaceTime video message), where <UUID> is the row's ZRECORDUUID.

Implementation notes

• Register beside PhoneService in ServerController.services, gated on the store's existence, so Macs without the macOS 26+ Phone app are unaffected.
• Follow the Phone/Messages access pattern: read-only SQLite with an immutable-URI fallback, plus a folder grant on the Data Store folder when the default path isn't readable (the write-ahead log and the Assets tree sit beside the database, so the grant has to cover the folder).
• First version reads the live store only. Reading voicemail out of unencrypted iPhone backups (Library/Voicemail/voicemail.db) could be a follow-up for Macs that don't run the Phone app.

I'd be happy to put together a PR for this.