- Added support for custom props in the sandbox, including loading, saving, and rendering.
- Implemented `PropLibrary` for managing custom prop entries and scanning for `.prop` files.
- Introduced `PropVisuals` for shared visual and collision representation of custom props.
- Enhanced `StageSpawner` to handle spawning of custom props with layered visuals and collision hulls.
- Created `MissingPropPlaceholder` to manage missing custom props during scene reloads.
- Updated thumbnail generation to support custom props with unique keys based on file paths.
- Added tests for custom prop lifecycle, authored visual values, and missing prop handling.
- Refactored existing code to accommodate new prop functionalities and ensure backward compatibility.
- Implement test for popup anchor behavior in rule-builder menus to ensure consistent anchor positioning during menu transitions.
- Create tests for stage logic, including mode transitions, toolbar visibility, and status bar updates.
- Add terrain drag-painting tests to verify correct block placement behavior and conflict handling.
- Introduce walk waypoint tests to check for arrival conditions and position stability after navigation.
ryan