- Platform.GetCurrent() for active screen query
- ScreenPlacement with Apply() for window positioning rules
- Rect geometry: Origin, Corner, InsideCorner, IsEmpty, Contains, RectSize, Intersect
- Point type, Alignment/OffsetReference constants
- 18 new tests with Good/Bad/Ugly coverage
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>