chore: checkpoint web Blender migration source, tools and docs

Accumulated uncommitted work: GHOST Web backend, WebGL/GPU web layer,
web workflow engine and protocol, tooling, docs and task records.
Large generated evidence, user-testing archives, build snapshots and
imported test assets remain untracked.

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

blender-5.2.0/extern/audaspace/plugins/ffmpeg/FFMPEG.cpp

@@ -18,6 +18,7 @@
 #include "FFMPEGReader.h"
 #include "FFMPEGWriter.h"
 #include "file/FileManager.h"
+#include "Exception.h"
 
 AUD_NAMESPACE_BEGIN
 
@@ -57,6 +58,14 @@ std::vector<StreamInfo> FFMPEG::queryStreams(std::shared_ptr<Buffer> buffer)
 
 std::shared_ptr<IWriter> FFMPEG::createWriter(const std::string &filename, DeviceSpecs specs, Container format, Codec codec, unsigned int bitrate)
 {
+#ifdef __EMSCRIPTEN__
+	// Preserve the linked libsndfile writer's CBR, Vorbis bitrate and PCM
+	// semantics. FFmpeg owns the additional containers and Ogg/FLAC only.
+	if(format != CONTAINER_AAC && format != CONTAINER_AC3 &&
+	   format != CONTAINER_MP2 && format != CONTAINER_MATROSKA &&
+	   !(format == CONTAINER_OGG && codec == CODEC_FLAC))
+		AUD_THROW(FileException, "This container uses the native libsndfile writer.");
+#endif
 	return std::shared_ptr<IWriter>(new FFMPEGWriter(filename, specs, format, codec, bitrate));
 }