Fix proxy decoding path and add proxy generation diagnostics

- RenderWorkerPool::DecodeInputFrame now uses the proxy filename/decoder/stream
  from FootageJob when a proxy is attached, so generated proxies are actually
  used during render.
- Add qDebug/qWarning logging to TimelineWidget::GenerateProxiesForSelectedClips
  and ProxyTask::Run to diagnose why Generate Proxy appears to do nothing.

app/render/renderworkerpool.cpp

@@ -145,6 +145,17 @@ FramePtr DecodeInputFrame(DecoderCache *decoder_cache,
 {
 	VideoParams stream_data = input.job.video_params();
 	QString filename = input.job.filename();
+	QString decoder_id = input.job.decoder();
+	int stream_index = stream_data.stream_index();
+
+	// Use generated proxy if one is attached to the job. The Footage node only
+	// attaches a proxy when it is enabled, ready, and matches this stream.
+	if (input.job.has_proxy()) {
+		filename = input.job.proxy_filename();
+		decoder_id = input.job.proxy_decoder();
+		stream_index = input.job.proxy_stream_index();
+	}
+
 	DecoderPtr decoder;
 
 	switch (stream_data.video_type()) {
@@ -152,17 +163,17 @@ FramePtr DecodeInputFrame(DecoderCache *decoder_cache,
 	case VideoParams::kVideoTypeStill:
 		decoder = ResolveDecoderFromCache(
 			decoder_cache,
-			input.job.decoder(),
-			Decoder::CodecStream(filename, stream_data.stream_index(), nullptr));
+			decoder_id,
+			Decoder::CodecStream(filename, stream_index, nullptr));
 		break;
 	case VideoParams::kVideoTypeImageSequence: {
 		const int64_t frame_number =
 			stream_data.get_time_in_timebase_units(input.time);
 		filename = Decoder::TransformImageSequenceFileName(filename, frame_number);
-		decoder = Decoder::CreateFromID(input.job.decoder());
+		decoder = Decoder::CreateFromID(decoder_id);
 		if (decoder &&
 			!decoder->Open(Decoder::CodecStream(filename,
-												stream_data.stream_index(),
+												stream_index,
 												nullptr))) {
 			decoder = nullptr;
 		}

app/task/proxy/proxy.cpp

@@ -1,20 +1,22 @@
-/*
- * Oak Video Editor - Non-Linear Video Editor
- * Copyright (C) 2026 Oak Team
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
+/***
+
+  Oak - Non-Linear Video Editor
+  Copyright (C) 2026 Oak Team
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+***/
 
 #include "proxy.h"
 
@@ -45,21 +47,27 @@ bool ProxyTask::Run()
 	const QString ffmpeg = QStandardPaths::findExecutable(QStringLiteral("ffmpeg"));
 	if (ffmpeg.isEmpty()) {
 		SetError(tr("Failed to generate proxy: ffmpeg executable was not found"));
+		qWarning() << "ProxyTask: ffmpeg executable not found";
 		return false;
 	}
 
 	QDir output_dir = QFileInfo(output_filename_).dir();
 	if (!output_dir.exists() && !output_dir.mkpath(QStringLiteral("."))) {
 		SetError(tr("Failed to create proxy output directory"));
+		qWarning() << "ProxyTask: failed to create output directory"
+				 << output_dir.absolutePath();
 		return false;
 	}
 
+	qDebug() << "ProxyTask: starting ffmpeg proxy generation:"
+			 << source_filename_ << "->" << output_filename_;
+
 	QFile::remove(output_filename_);
 
 	const QString scale_filter = QStringLiteral(
 		"scale=w=%1:h=%2:force_original_aspect_ratio=decrease")
-							.arg(QString::number(params_.width),
-								 QString::number(params_.height));
+							 .arg(QString::number(params_.width),
+								  QString::number(params_.height));
 
 	QStringList args;
 	args << QStringLiteral("-y")
@@ -82,6 +90,7 @@ bool ProxyTask::Run()
 
 	if (!process.waitForStarted()) {
 		SetError(tr("Failed to start ffmpeg for proxy generation"));
+		qWarning() << "ProxyTask: failed to start ffmpeg" << process.errorString();
 		return false;
 	}
 
@@ -99,14 +108,19 @@ bool ProxyTask::Run()
 		const QString output = QString::fromUtf8(process.readAll()).trimmed();
 		QFile::remove(output_filename_);
 		SetError(tr("ffmpeg failed to generate proxy: %1").arg(output));
+		qWarning() << "ProxyTask: ffmpeg failed with exit code" << process.exitCode()
+				 << "output:" << output;
 		return false;
 	}
 
 	if (!QFileInfo::exists(output_filename_)) {
 		SetError(tr("ffmpeg finished but proxy file was not created"));
+		qWarning() << "ProxyTask: ffmpeg finished but output file missing"
+				 << output_filename_;
 		return false;
 	}
 
+	qDebug() << "ProxyTask: proxy generation succeeded:" << output_filename_;
 	emit ProgressChanged(1.0);
 	return true;
 }

app/widget/timelinewidget/timelinewidget.cpp

@@ -1182,13 +1182,16 @@ void TimelineWidget::SynchronizeSelectedClipsByWaveform()
 void TimelineWidget::GenerateProxiesForSelectedClips()
 {
 	if (!ProxyManager::instance() || !sequence()) {
+		qWarning() << "GenerateProxiesForSelectedClips: ProxyManager or sequence unavailable";
 		return;
 	}
 
 	const QVector<Footage *> footage = GetSelectedProxyFootage(selected_blocks_);
+	qDebug() << "GenerateProxiesForSelectedClips: starting proxy generation for" << footage.size() << "footage item(s)";
 	for (Footage *item : footage) {
 		const VideoParams video = item->GetFirstEnabledVideoStream();
 		if (!video.is_valid()) {
+			qWarning() << "GenerateProxiesForSelectedClips: skipping item with no valid video stream" << item->filename();
 			continue;
 		}
 
@@ -1197,6 +1200,9 @@ void TimelineWidget::GenerateProxiesForSelectedClips()
 			ProxyManager::instance()->GetOrStartProxy(
 				item->project()->cache_path(), item->filename(),
 				video.stream_index(), params);
+		qDebug() << "GenerateProxiesForSelectedClips: proxy state=" << ProxyManager::ProxyStateToString(proxy.state)
+				 << "file=" << proxy.filename
+				 << "cache=" << item->project()->cache_path();
 		item->SetProxy(proxy.filename, proxy.state, video.stream_index(),
 					   params.version, true);
 		item->InvalidateAll(Footage::kFilenameInput);