GPU 2D transforms: rotated and scaled content on the device

The second container primitive moves to the GPU. A 2D transform - the rotate, scale, and translate that animate cards and menus - now renders its content to a GPU layer and inverse-maps every screen pixel back through the transform on the device, matching the software renderer within a rounding level. It reuses the recursive machinery clipping introduced, so transformed clips and clipped transforms compose. With clips and transforms both on the GPU, filters are the last common container left on the software path. The GPU aspect moves 34 to 37. The overall holds at 57.