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>

web/protocol/paint.ts

@@ -150,7 +150,8 @@ export function createSculptMeshAttributes(
     faceCount,
     mask: Array.from({ length: vertexCount }, () => maskValue),
     faceSets: Array.from({ length: faceCount }, () => faceSet),
-    activeFaceSet: faceSet,
+    // The active face is transient Sculpt session state, not a Mesh attribute.
+    activeFaceSet: -1,
     revision,
   };
 }