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>

tools/web/patches/cpython-3.13-webengine-unraisable.patch

@@ -0,0 +1,32 @@
+--- a/Python/errors.c
++++ b/Python/errors.c
+@@ -1584,6 +1584,15 @@
+ 
+    An exception must be set when calling this function. */
+ 
++#ifdef __EMSCRIPTEN__
++/* Optional native embedder notification, before allocation, exception
++ * normalization, audit hooks or sys.unraisablehook. The embedder must not call
++ * Python or retain the exception. Standalone CPython keeps its usual behavior.
++ * This also covers a deleted sys.unraisablehook and hook-argument OOM. */
++extern void web_engine_python_unraisable(const char *exception_type)
++    __attribute__((weak));
++#endif
++
+ static void
+ format_unraisable_v(const char *format, va_list va, PyObject *obj)
+ {
+@@ -1598,6 +1607,13 @@
+     PyObject *exc_type, *exc_value, *exc_tb;
+     _PyErr_Fetch(tstate, &exc_type, &exc_value, &exc_tb);
+ 
++#ifdef __EMSCRIPTEN__
++    if (web_engine_python_unraisable != NULL) {
++        web_engine_python_unraisable(
++            exc_type != NULL && PyType_Check(exc_type)
++                ? ((PyTypeObject *)exc_type)->tp_name : NULL);
++    }
++#endif
+     assert(exc_type != NULL);
+ 
+     if (exc_type == NULL) {

tools/web/patches/libsndfile-vorbis-bitrate.patch

@@ -0,0 +1,142 @@
+--- a/include/sndfile.h
++++ b/include/sndfile.h
+@@ -229,6 +229,9 @@
+ 	SFC_GET_BITRATE_MODE			= 0x1304,
+ 	SFC_SET_BITRATE_MODE			= 0x1305,
+ 
++	/* WebEngine extension: int target bits/s, native Vorbis managed encoding. */
++	SFC_WEB_SET_VORBIS_BITRATE		= 0x7B01,
++
+ 	/* Cart Chunk support */
+ 	SFC_SET_CART_INFO				= 0x1400,
+ 	SFC_GET_CART_INFO				= 0x1401,
+--- a/src/ogg_vorbis.c
++++ b/src/ogg_vorbis.c
+@@ -137,6 +137,9 @@
+ 	vorbis_block vblock ;
+ 	/* Encoding quality in range [0.0, 1.0]. */
+ 	double quality ;
++	/* WebEngine: zero keeps upstream VBR quality mode. */
++	int nominal_bitrate ;
++	int header_ready ;
+ 	/* Offset of the first samples' granule position. */
+ 	uint64_t pcm_start ;
+ 	/* Last valid samples' granule position. */
+@@ -313,20 +316,22 @@
+ 	VORBIS_PRIVATE *vdata = (VORBIS_PRIVATE *) psf->codec_data ;
+ 	int k, ret ;
+ 
++	if (vdata->header_ready)
++		return 0 ;
++
+ 	vorbis_info_init (&vdata->vinfo) ;
+ 
+-	/* The style of encoding should be selectable here, VBR quality mode. */
+-	ret = vorbis_encode_init_vbr (&vdata->vinfo, psf->sf.channels, psf->sf.samplerate, vdata->quality) ;
+-
+-#if 0
+-	ret = vorbis_encode_init (&vdata->vinfo, psf->sf.channels, psf->sf.samplerate, -1, 128000, -1) ; /* average bitrate mode */
+-	ret = (	vorbis_encode_setup_managed (&vdata->vinfo, psf->sf.channels, psf->sf.samplerate, -1, 128000, -1)
+-			|| vorbis_encode_ctl (&vdata->vinfo, OV_ECTL_RATEMANAGE_AVG, NULL)
+-			|| vorbis_encode_setup_init (&vdata->vinfo)
+-			) ;
+-#endif
++	/* Select libvorbis' original managed average bitrate encoder when requested.
++	** No bitrate-to-quality approximation: the native codec owns rate control. */
++	if (vdata->nominal_bitrate > 0)
++		ret = vorbis_encode_init (&vdata->vinfo, psf->sf.channels, psf->sf.samplerate,
++				-1, vdata->nominal_bitrate, -1) ;
++	else
++		ret = vorbis_encode_init_vbr (&vdata->vinfo, psf->sf.channels, psf->sf.samplerate, vdata->quality) ;
+ 	if (ret)
++	{	vorbis_info_clear (&vdata->vinfo) ;
+ 		return SFE_BAD_OPEN_FORMAT ;
++		} ;
+ 
+ 	vdata->gp = 0 ;
+ 
+@@ -395,6 +400,7 @@
+ 			} ;
+ 	}
+ 
++	vdata->header_ready = SF_TRUE ;
+ 	return 0 ;
+ } /* vorbis_write_header */
+ 
+@@ -402,6 +408,7 @@
+ vorbis_close (SF_PRIVATE *psf)
+ {	OGG_PRIVATE* odata = psf->container_data ;
+ 	VORBIS_PRIVATE *vdata = psf->codec_data ;
++	int error = 0 ;
+ 
+ 	if (odata == NULL || vdata == NULL)
+ 		return 0 ;
+@@ -411,8 +418,10 @@
+ 
+ 	if (psf->file.mode == SFM_WRITE)
+ 	{
+-		if (psf->write_current <= 0)
+-			vorbis_write_header (psf, 0) ;
++		/* A rejected rate/rate-channel combination must never drain an
++		** uninitialized encoder or leak its native allocations on close. */
++		if (! vdata->header_ready && (error = vorbis_write_header (psf, 0)))
++			goto cleanup ;
+ 
+ 		vorbis_analysis_wrote (&vdata->vdsp, 0) ;
+ 		while (vorbis_analysis_blockout (&vdata->vdsp, &vdata->vblock) == 1)
+@@ -441,6 +450,7 @@
+ 		}
+ 	}
+ 
++cleanup:
+ 	/* ogg_page and ogg_packet structs always point to storage in
+ 	   libvorbis.  They are never freed or manipulated directly */
+ 
+@@ -449,7 +459,7 @@
+ 	vorbis_comment_clear (&vdata->vcomment) ;
+ 	vorbis_info_clear (&vdata->vinfo) ;
+ 
+-	return 0 ;
++	return error ;
+ } /* vorbis_close */
+ 
+ int
+@@ -515,12 +525,36 @@
+ 	VORBIS_PRIVATE *vdata = (VORBIS_PRIVATE *) psf->codec_data ;
+ 
+ 	switch (command)
+-	{	case SFC_SET_COMPRESSION_LEVEL :
++	{	case SFC_WEB_SET_VORBIS_BITRATE :
++		{	vorbis_info candidate ;
++			int bitrate, result ;
++			if (psf->file.mode != SFM_WRITE || psf->have_written || vdata->header_ready ||
++				data == NULL || datasize != sizeof (int))
++				return SF_FALSE ;
++			bitrate = *((int *) data) ;
++			if (bitrate <= 0)
++				return SF_FALSE ;
++
++			/* Ask the same encoder to accept the complete rate/channel tuple
++			** before retaining it. A failed command leaves settings unchanged. */
++			vorbis_info_init (&candidate) ;
++			result = vorbis_encode_init (&candidate, psf->sf.channels, psf->sf.samplerate,
++					-1, bitrate, -1) ;
++			vorbis_info_clear (&candidate) ;
++			if (result)
++				return SF_FALSE ;
++			vdata->nominal_bitrate = bitrate ;
++			return SF_TRUE ;
++			} ;
++
++		case SFC_SET_COMPRESSION_LEVEL :
+ 			if (data == NULL || datasize != sizeof (double))
+ 				return SF_FALSE ;
+ 
+-			if (psf->have_written)
++			if (psf->file.mode != SFM_WRITE || psf->have_written || vdata->header_ready)
+ 				return SF_FALSE ;
++
++			vdata->nominal_bitrate = 0 ;
+ 
+ 			vdata->quality = 1.0 - *((double *) data) ;
+