chore: checkpoint web Blender feature-gap work, docs and tests

- update native web_engine sources and rebuilt wasm artifacts
- add task cards, status notes and tooling scripts
- add web e2e specs, tutorial UI sources and tutorial assets
- sync golden task manifests and audit records

Co-Authored-By: Claude Code <noreply@anthropic.com>

blender-5.2.0/source/blender/blenkernel/intern/blender.cc

@@ -253,6 +253,9 @@ Main *BKE_blender_globals_main_swap(Main *new_gmain)
 #endif
   new_gmain->is_global_main = true;
   G_MAIN = new_gmain;
+#ifdef WITH_WEB
+  RNAMainAccessScope::restore_after_temporary_main_swap(new_gmain);
+#endif
   old_gmain->is_global_main = false;
   return old_gmain;
 }