Render an interactive Scene Graph in the Settings panel using @visual-json/react. Introduces SceneNode/SceneGraphNode types and buildSceneGraphValue to build a tree (handles missing nodes and cycles), and adds handlers to block drag/drop/context/delete mutations inside the viewer. Adds @visual-json/react to apps/editor package.json and updates the dev script to forbid .env.local and source the root .env instead. Also adds a persistence migration in use-scene to preserve existing nodes and rootNodeIds when the persist version changes.
