- Position is now { x, y, z }; higher z draws on top, ties keep hierarchy order
- Viewport sorts the objects layer deterministically (syncDrawOrder)
- Inspector shows a Z field; asset properties that differ from the schema
default are marked bold with a reset button (ResetAssetPropertyCommand)
- isModified() helper, unit tests, E2E checks and seed updated
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>