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/source/blender/blenkernel/intern/appdir.cc

@@ -837,7 +837,9 @@ std::optional<std::string> BKE_appdir_folder_id_create(const int folder_id, cons
   if (!path.has_value()) {
     path = BKE_appdir_folder_id_user_notest(folder_id, subfolder);
     if (path.has_value()) {
-      BLI_dir_create_recursive(path->c_str());
+      if (!BLI_dir_create_recursive(path->c_str())) {
+        return std::nullopt;
+      }
     }
   }