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>

my-tools/build_local_webengine.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""Incrementally compile the local WebEngine and publish its integrity binding."""
+import json
+import os
+from pathlib import Path
+import shutil
+import subprocess
+import time
+
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+def main():
+    nodes = sorted((ROOT / ".emsdk/node").glob("*/bin/node"))
+    node = str(nodes[-1]) if nodes else shutil.which("node")
+    if not node:
+        raise RuntimeError("local Node executable missing")
+    environment = {**os.environ,
+        "EM_CONFIG": str(ROOT / ".emscripten-web"),
+        "EM_LLVM_ROOT": str(ROOT / ".emsdk/upstream/bin"),
+        "EM_BINARYEN_ROOT": str(ROOT / ".emsdk/upstream"),
+        "EM_NODE_JS": node,
+        "EM_LLVM_ADD_VERSION": "", "EM_CLANG_ADD_VERSION": "",
+    }
+    jobs = max(1, min(4, int(os.environ.get("CMAKE_BUILD_PARALLEL_LEVEL", "4"))))
+    stages = []
+    for name, argv in [
+        ("incremental_compile", ["cmake", "--build", "build_web_blender6", "--target", "web_engine", "--parallel", str(jobs)]),
+        ("runtime_integrity_sync", ["node", "tools/web/sync-web-engine-runtime.mjs"]),
+    ]:
+        start = time.monotonic()
+        result = subprocess.run(argv, cwd=ROOT, env=environment)
+        stages.append({"stage": name, "seconds": round(time.monotonic() - start, 6), "exitCode": result.returncode})
+        print(json.dumps(stages[-1]), flush=True)
+        if result.returncode:
+            return result.returncode
+    if os.environ.get("WBV2_RECEIPT_DIR"):
+        output = Path(os.environ["WBV2_RECEIPT_DIR"])
+        output.mkdir(parents=True, exist_ok=True)
+        (output / "build-stages.json").write_text(json.dumps(stages, indent=2) + "\n", encoding="utf-8")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())