feat(domain): ProgressStep.Note; UploadErrIncomplete removed -- a short file is noted, not refused (second review finding 1)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/domain/domain.go

@@ -203,6 +203,10 @@ type ProgressStep struct {
 	FinishedAt time.Time `json:"finished_at,omitzero"`
 	Done       int       `json:"done,omitempty"`
 	Total      int       `json:"total,omitempty"`
+	// Note is a short plain remark about the phase that the reader should see even though
+	// it did not fail, for example that the audio is much shorter than the file claimed.
+	// Durations and counts only: never transcript text, a name or a path.
+	Note string `json:"note,omitempty"`
 }
 
 // UploadStatus is the state of an uploaded-audio transcription job.
@@ -233,10 +237,6 @@ const (
 	// UploadErrBusy: too many recordings were already waiting, so this one was not
 	// queued. The user's to retry later (ADR-035 review).
 	UploadErrBusy UploadErrorKind = "queue_full"
-	// UploadErrIncomplete: the audio, once converted, ends far earlier than the file
-	// claimed: a truncated recording that would otherwise give a partial transcript with
-	// no warning.
-	UploadErrIncomplete UploadErrorKind = "audio_incomplete"
 )
 
 // UploadedTranscript is a user's PRIVATE transcript of audio they uploaded. It is