Checkpoint 2: integrate native Editor, MCP, gameplay builds and standalone export

include/faset/authoring/transforms.hpp

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+#pragma once
+#include <faset/core/json.hpp>
+#include <string>
+namespace faset::authoring {
+// Reparents authored TRS while optionally preserving the complete world transform.
+// Non-invertible parents and transforms requiring shear are rejected atomically.
+void reparent_entity(Json& scene, const std::string& entity, const Json& parent, bool keep_world);
+} // namespace faset::authoring