fix: audio clip items lost after reload — missing serverFileId on clip/track

- set serverFileId on clip + track when upload succeeds
- serialize/deserialize server_file_id in source_data
- guard clip.buffer null in WaveformLane canvas draw

app/static/js/app.jsx

@@ -1376,6 +1376,7 @@ const WaveformLane = ({
 
     if (clips.length > 0) {
       clips.forEach(clip => {
+        if (!clip.buffer) return;
         const numChannels = clip.buffer.numberOfChannels || 1;
         const dataL = clip.buffer.getChannelData(0);
         const dataR = numChannels >= 2 ? clip.buffer.getChannelData(1) : dataL;
@@ -7548,6 +7549,7 @@ const serializeTracksList = (tracksList, secondsPerBar) => {
     if (trackType === "AUDIO" && t.clips) {
       t.clips.forEach(c => {
         const durationSec = c.buffer ? c.buffer.duration : 4.0;
+        const clipFileId = c.serverFileId || t.serverFileId;
         items.push({
           id: c.id,
           name: c.name || "Audio Clip",
@@ -7556,10 +7558,11 @@ const serializeTracksList = (tracksList, secondsPerBar) => {
           duration_bars: (durationSec / (c.speed || 1.0)) / secondsPerBar,
           clip_start_offset_bars: 0.0,
           source_data: {
-            audio_file_url: t.serverFileId ? `/static/audio/uploads/${t.serverFileId}` : "",
+            audio_file_url: clipFileId ? `/static/audio/uploads/${clipFileId}` : "",
             sample_rate: c.buffer ? c.buffer.sampleRate : 44100,
             channels: c.buffer ? c.buffer.numberOfChannels : 2,
-            gain: 1.0
+            gain: 1.0,
+            server_file_id: clipFileId
           }
         });
       });
@@ -7631,11 +7634,13 @@ const deserializeTracksList = (schemaTracks, secondsPerBar, sectionStore) => {
     (t.items || []).forEach(item => {
       if (item.type === "AUDIO_ITEM") {
         const src = item.source_data || {};
+        const clipFileId = src.server_file_id || null;
         clips.push({
           id: item.id,
           name: item.name,
           startTime: item.start_bar * secondsPerBar,
-          speed: 1.0
+          speed: 1.0,
+          serverFileId: clipFileId
         });
       } else if (item.type === "MIDI_ITEM") {
         const src = item.source_data || {};
@@ -7683,7 +7688,7 @@ const deserializeTracksList = (schemaTracks, secondsPerBar, sectionStore) => {
       startTime: t.start_time || 0,
       height: t.height || 140,
       markers: t.markers || [],
-      serverFileId: t.server_file_id || (t.items && t.items.find(function(i) { return i.type === 'AUDIO_ITEM'; })?.source_data?.audio_file_url?.split('/').pop()) || null,
+      serverFileId: t.server_file_id || (t.items && t.items.find(function(i) { return i.type === 'AUDIO_ITEM'; })?.source_data?.server_file_id) || (t.items && t.items.find(function(i) { return i.type === 'AUDIO_ITEM'; })?.source_data?.audio_file_url?.split('/').pop()) || null,
       channelInfo: t.channel_info || null,
       isArmed: t.is_armed || false,
       monitoringEnabled: t.monitoring_enabled !== false,
@@ -15775,13 +15780,15 @@ const App = () => {
       let count = 0;
       for (const file of files) {
         try {
-          uploadToServer(file, track.id);
+          const uploadResult = await uploadToServer(file, track.id);
+          const fileId = uploadResult?.file_id || null;
           const { audioBuffer: decodedBuffer, channelInfo } = await window.SonicAudio.decodeAudioFile(file);
           const clipId = `clip_${Date.now()}_${Math.random().toString(36).slice(2, 6)}`;
-          const newClip = { id: clipId, buffer: decodedBuffer, startTime: offset, name: file.name, speed: 1.0 };
+          const newClip = { id: clipId, buffer: decodedBuffer, startTime: offset, name: file.name, speed: 1.0, serverFileId: fileId };
           createClipWithUndo(selectedTrackId, newClip);
           updateActiveTracks(prev => prev.map(t => t.id === selectedTrackId ? {
             ...t,
+            serverFileId: t.serverFileId || fileId,
             clips: [...(t.clips || []), newClip]
           } : t));
           offset += decodedBuffer.duration;