- Introduced StageGizmos for hover highlighting, selection outlines, and rotation handles in the sandbox stage builder.
- Added StageGrid for an optional world-space grid overlay that adjusts with camera panning and zooming.
- Implemented StageSelection for geometric hit-testing and selection management of nodes in the sandbox.
- Created StageSpawner as a registry-driven factory for spawning terrain, props, and stickmen, allowing for dynamic template management.
- Each script includes necessary constants, state management, and public API methods for interaction.
