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/build-webengine-ffmpeg.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+"""Build Blender-pinned FFmpeg audio libraries for the embedded Audaspace plugin."""
+
+import argparse
+import hashlib
+import json
+import os
+from pathlib import Path
+import shutil
+import subprocess
+import tarfile
+import urllib.request
+
+ROOT = Path(__file__).resolve().parents[2]
+VERSION = "8.1"
+SHA256 = "c07039598df7d64d3c8b42c4e25b1959fc908621c6f6c2946881133f3b27eda2"
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--source", type=Path)
+    parser.add_argument("--jobs", type=int, default=3)
+    args = parser.parse_args()
+    base = ROOT / "build_web_ffmpeg"
+    base.mkdir(exist_ok=True)
+    source = args.source.resolve() if args.source else base / f"ffmpeg-{VERSION}"
+    if not (source / "configure").is_file():
+        if args.source:
+            raise FileNotFoundError(source)
+        filename = f"ffmpeg-{VERSION}.tar.bz2"
+        caches = [base / filename, Path.home() / "working/packages" / filename,
+                  Path.home() / "working/build_oiio_deps/downloads" / filename]
+        archive = next((path for path in caches if path.is_file()), caches[0])
+        if not archive.is_file():
+            partial = archive.with_suffix(".partial")
+            with urllib.request.urlopen(f"https://ffmpeg.org/releases/{filename}", timeout=60) as response, partial.open("wb") as out:
+                shutil.copyfileobj(response, out)
+            partial.replace(archive)
+        if hashlib.sha256(archive.read_bytes()).hexdigest() != SHA256:
+            raise RuntimeError("Blender-pinned FFmpeg archive digest mismatch")
+        with tarfile.open(archive) as package:
+            package.extractall(base, filter="data")
+    if (source / "RELEASE").read_text().strip() != VERSION:
+        raise RuntimeError("Expected Blender-pinned FFmpeg " + VERSION)
+    prefix = base / "install"
+    build = base / "build"
+    build.mkdir(exist_ok=True)
+    em = ROOT / ".emsdk/upstream/emscripten"
+    codecs = ROOT / "build_web_sndfile/install"
+    env = dict(os.environ)
+    env["PATH"] = str(em) + os.pathsep + env["PATH"]
+    env["PKG_CONFIG_LIBDIR"] = str(codecs / "lib/pkgconfig")
+    env["PKG_CONFIG_PATH"] = ""
+    command = [str(source / "configure"), f"--prefix={prefix}",
+               "--target-os=none", "--arch=wasm32", "--enable-cross-compile",
+               "--cc=" + str(em / "emcc"), "--cxx=" + str(em / "em++"),
+               "--ar=" + str(em / "emar"), "--ranlib=" + str(em / "emranlib"),
+               "--nm=" + str(em.parent / "bin/llvm-nm"),
+               f"--extra-cflags=-O2 -fPIC -I{codecs / 'include'}",
+               f"--extra-ldflags=-L{codecs / 'lib'}", "--disable-asm", "--disable-x86asm",
+               "--disable-pthreads", "--disable-w32threads", "--disable-os2threads",
+               "--disable-network", "--disable-autodetect", "--disable-everything",
+               "--disable-programs", "--disable-doc", "--disable-debug",
+               "--disable-avdevice", "--disable-avfilter", "--disable-swscale",
+               "--disable-shared", "--enable-static", "--enable-small",
+               "--enable-protocol=file", "--enable-libmp3lame", "--enable-libopus",
+               "--enable-libvorbis", "--pkg-config-flags=--static",
+               "--enable-encoder=aac,ac3,mp2,flac,libmp3lame,libopus,libvorbis,pcm_u8,pcm_s16le,pcm_s24le,pcm_s32le,pcm_f32le,pcm_f64le",
+               "--enable-decoder=aac,ac3,mp2,mp3,flac,opus,vorbis,pcm_u8,pcm_s16le,pcm_s24le,pcm_s32le,pcm_f32le,pcm_f64le",
+               "--enable-parser=aac,ac3,mpegaudio,flac,opus,vorbis",
+               "--enable-muxer=adts,ac3,mp2,mp3,flac,matroska,ogg,wav",
+               "--enable-demuxer=aac,ac3,mp3,flac,matroska,ogg,wav,mov",
+               "--enable-bsf=aac_adtstoasc,extract_extradata"]
+    settings = json.dumps([command, env["PKG_CONFIG_LIBDIR"]])
+    stamp = build / "web-configure.json"
+    if not stamp.is_file() or stamp.read_text() != settings:
+        subprocess.run(command, cwd=build, env=env, check=True)
+        stamp.write_text(settings)
+    subprocess.run(["make", f"-j{args.jobs}", "install"], cwd=build, env=env, check=True)
+    artifacts = {str(path.relative_to(ROOT)): hashlib.sha256(path.read_bytes()).hexdigest()
+                 for path in sorted((prefix / "lib").glob("*.a"))}
+    (base / "build-manifest.json").write_text(json.dumps({
+        "version": VERSION, "source": str(source), "upstreamArchiveSha256": SHA256,
+        "configure": command, "artifacts": artifacts,
+        "validation": "NOT_RUN", "acceptance": "NOT_CLAIMED"}, indent=2) + "\n")
+
+
+if __name__ == "__main__":
+    main()