docs: reflect DurationSeconds write on replace-audio

Replace path now updates SQL DurationSeconds via unconditional SetDuration; document SetDuration vs null-guarded UpdateDuration and correct the stale 'SQL is not written' note.

DeepDrftAPI/CLAUDE.md

@@ -178,7 +178,7 @@ Soft-delete a release row. Used by the albums browser to remove an orphaned rele
 - **Route parameter `id`** (long): the SQL track ID.
 - **Form field `audioFile`** (`IFormFile`, required): the replacement audio bytes. File name must end in `.wav`, `.mp3`, or `.flac`.
 - `[RequestSizeLimit(1 GB)]` + `[RequestFormLimits(MultipartBodyLengthLimit = 1 GB)]` mirror the upload ceiling. The body is streamed to a temp file (correct extension preserved for the audio processor), always deleted in a `finally` block.
-- Calls `UnifiedTrackService.ReplaceAudioAsync`, which: looks up SQL row by id → calls `TrackContentService.ReplaceTrackAudioAsync(entryKey, tempFilePath)` (registers new audio under the existing `EntryKey`; removes the stale backing file only on a cross-format swap, after the new write succeeds) → regenerates both waveform datums. SQL is not written.
+- Calls `UnifiedTrackService.ReplaceAudioAsync`, which: looks up SQL row by id → calls `TrackContentService.ReplaceTrackAudioAsync(entryKey, tempFilePath)` (registers new audio under the existing `EntryKey`; removes the stale backing file only on a cross-format swap, after the new write succeeds) → regenerates both waveform datums (best-effort; a datum failure is logged and swallowed) → writes the new audio's duration to `DurationSeconds` via `ITrackService.SetDuration` (unconditional overwrite; a failure is surfaced, not swallowed, to prevent derived aggregates like `MixRuntimeSeconds` from silently going stale).
 - Returns 200 on success. Returns 400 if the file is missing or the format is unsupported. Returns 404 if the track id is not found. Returns 500 if vault processing fails.
 
 ### GET api/track/page (unauthenticated)