Remove noisy graph-snapshot logs and add waveform-sync diagnostics

- Strip the dense RenderWorkerPool debug messages about cached/stale graph
  snapshots and cleanup to reduce log spam.
- Add qDebug logging and status-bar feedback to
  TimelineWidget::SynchronizeSelectedClipsByWaveform() so we can see why the
  sync action does nothing (e.g. not enough cached clips or no usable offset).

app/render/renderworkerpool.cpp

@@ -579,14 +579,8 @@ bool RenderWorkerPool::PrepareJob(RenderTicketPtr ticket,
 		if (it != graph_cache_.end() && !project->is_modified()) {
 			graph_path = it->path;
 			AddGraphPathRefLocked(graph_path);
-			qDebug()
-				<< "RenderWorkerPool::PrepareJob: using cached graph snapshot"
-				<< graph_path;
 		} else {
 			if (it != graph_cache_.end()) {
-				qDebug()
-					<< "RenderWorkerPool::PrepareJob: graph stale, rewriting"
-					<< project->is_modified();
 				SetGraphPathCachedLocked(it->path, false);
 				graph_cache_.erase(it);
 			}
@@ -648,9 +642,6 @@ bool RenderWorkerPool::WriteGraphSnapshot(Project *project, QString *path)
 		return false;
 	}
 
-	qDebug() << "RenderWorkerPool wrote graph snapshot" << file.fileName()
-			 << "size" << QFileInfo(file.fileName()).size();
-
 	*path = file.fileName();
 	return true;
 }
@@ -1242,7 +1233,6 @@ void RenderWorkerPool::FinishWithFrame(RenderTicketPtr ticket,
 void RenderWorkerPool::CleanupGraphFile(const QString &path)
 {
 	if (!path.isEmpty()) {
-		qDebug() << "RenderWorkerPool cleaning up graph file" << path;
 		QFile::remove(path);
 	}
 }

app/widget/timelinewidget/timelinewidget.cpp

@@ -1029,7 +1029,11 @@ void TimelineWidget::SynchronizeSelectedClipsByWaveform()
 
 	const QVector<WaveformSyncClip> sync_clips =
 		GetSelectedWaveformSyncClips(GetSelectedBlocks());
+	qDebug() << "TimelineWidget::SynchronizeSelectedClipsByWaveform:"
+			 << sync_clips.size() << "sync clip(s) selected";
 	if (sync_clips.size() < 2) {
+		Core::instance()->ShowStatusBarMessage(
+			tr("Select at least 2 clips with cached waveforms to sync by waveform"));
 		return;
 	}
 
@@ -1050,6 +1054,11 @@ void TimelineWidget::SynchronizeSelectedClipsByWaveform()
 	const QVector<double> reference_envelope =
 		ExtractWaveformCacheEnvelope(reference, sample_rate, window_samples);
 
+	qDebug() << "TimelineWidget::SynchronizeSelectedClipsByWaveform: sample_rate="
+			 << sample_rate << "window_samples=" << window_samples
+			 << "max_offset_windows=" << max_offset_windows
+			 << "reference_envelope_size=" << reference_envelope.size();
+
 	struct SyncPlacement {
 		ClipBlock *clip = nullptr;
 		rational timeline_in;
@@ -1069,6 +1078,11 @@ void TimelineWidget::SynchronizeSelectedClipsByWaveform()
 																  candidate_envelope,
 																  window_samples,
 																  max_offset_windows);
+		qDebug() << "TimelineWidget::SynchronizeSelectedClipsByWaveform: candidate"
+				 << sync_clip.clip << "envelope_size="
+				 << candidate_envelope.size() << "offset_valid="
+				 << offset.valid << "offset_samples=" << offset.offset_samples
+				 << "confidence=" << offset.confidence;
 		if (!offset.valid) {
 			continue;
 		}
@@ -1076,12 +1090,19 @@ void TimelineWidget::SynchronizeSelectedClipsByWaveform()
 		const AudioSynchronizer::Placement placement =
 			AudioSynchronizer::PlaceByWaveformOffset(
 				reference.clip->in(), offset.offset_samples, sample_rate);
+		qDebug() << "TimelineWidget::SynchronizeSelectedClipsByWaveform: placement"
+				 << "valid=" << placement.valid << "timeline_in="
+				 << placement.timeline_in.toDouble();
 		if (placement.valid && placement.timeline_in >= 0) {
 			placements.append({ sync_clip.clip, placement.timeline_in });
 		}
 	}
 
 	if (placements.size() < 2) {
+		qDebug() << "TimelineWidget::SynchronizeSelectedClipsByWaveform: no usable"
+				 << "offsets found";
+		Core::instance()->ShowStatusBarMessage(
+			tr("Could not find a usable waveform offset for the selected clips"));
 		return;
 	}
 
@@ -1108,6 +1129,8 @@ void TimelineWidget::SynchronizeSelectedClipsByWaveform()
 
 	Core::instance()->undo_stack()->push(command,
 													 tr("Synchronize Clips by Waveform"));
+	Core::instance()->ShowStatusBarMessage(
+		tr("Synchronized %1 clip(s) by waveform").arg(placements.size()));
 }
 
 void TimelineWidget::GenerateProxiesForSelectedClips()