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

Notes/Services/TranscriptionService.swift

@@ -117,7 +117,12 @@ final class TranscriptionService {
         try await syncEngine.applyTranscription(
             id: job.noteID,
             text: text,
-            localeID: TranscriptionSettings.canonicalID(locale)
+            localeID: TranscriptionSettings.canonicalID(locale),
+            // Real mean confidence when the engine attributed any runs; nil for
+            // a confidence-less engine so it's never mistaken for a measured 0.
+            confidence: LanguagePicker.hasConfidence(of: transcript)
+                ? LanguagePicker.meanConfidence(of: transcript) : nil,
+            languageWasForced: job.forcedLocaleID != nil
         )
     }