Decouple transcripts from note text; end-to-end watch transfer acks

Schema v3: transcription attempts accumulate on AudioInfo (text, locale,
confidence, forced flag) — latest attempt is displayed, payload.text is
purely user writing, v2 notes migrate at read time. Editor shows the
transcript in its own live-updating section with insert-into-note; search
matches transcripts weighted by confidence. Watch recordings are now
deleted only on the phone's durable-ingest ack (transferUserInfo), closing
every phone-side loss window; failed sidecar writes unstage instead of
orphaning, and unreadable inbox recordings are surfaced in logs.

Claude-Session: https://claude.ai/code/session_014esDWi42URLEC6Cj17hGQ3

Shared/Connectivity/AudioNotePayload.swift

@@ -71,3 +71,41 @@ struct AudioNotePayload: Equatable, Sendable {
         self.timeZoneID = metadata[Key.timeZone] as? String
     }
 }
+
+/// Phone → watch acknowledgment that a recording reached a terminal state on
+/// the phone (durably ingested into the iCloud container, or permanently
+/// vetoed). Sent over `transferUserInfo` — queued and durable, so an ack
+/// survives both apps being closed. **Only** this ack lets the watch delete
+/// its local copy of a recording; WatchConnectivity-level delivery success is
+/// deliberately not trusted, because the phone can still fail after `didReceive`
+/// returns (a staging or iCloud write failure would otherwise lose the audio
+/// forever — the watch's copy is the last line of defense).
+struct IngestAck: Equatable, Sendable {
+    static let currentVersion = 1
+
+    /// ULID string of the acknowledged recording.
+    let id: String
+
+    private enum Key {
+        static let version = "ackV"
+        static let id = "ackID"
+    }
+
+    init(id: String) {
+        self.id = id
+    }
+
+    /// A plist-serializable dictionary for `WCSession.transferUserInfo(_:)`.
+    func userInfo() -> [String: Any] {
+        [Key.version: Self.currentVersion, Key.id: id]
+    }
+
+    /// Decode a received userInfo dictionary; nil when it isn't an ack this
+    /// build understands (same forward-gate shape as `AudioNotePayload`).
+    init?(userInfo: [String: Any]) {
+        guard let version = userInfo[Key.version] as? Int,
+              version >= 1, version <= Self.currentVersion,
+              let id = userInfo[Key.id] as? String else { return nil }
+        self.id = id
+    }
+}