Unity scenes in the editor

Imported scenes become editor objects: built without running anything, written in the scene format (built-in settings that differ from a new component's, every script field), then destroyed. Scene references become {"ref": id}, project assets {"asset": "guid:fileID"}, resolved again on load.
The round trip is checked by conformance: cargo xtask conformance runs a second time with Unity scenes loaded through the editor form, and unity_import still matches Unity's recording.
MCP scene_open on a Unity project or scene opens it for editing (scene_query, scene_edit, undo) and plays the edited scene with the project's scripts, settings and assets; an e2e test edits Coin Dash's level into a one-coin race.
Next: saving back to .unity (keeping prefab links), FBX meshes and sub-assets by file ID, ScriptableObjects, .asmdef assemblies, then hot reload.