Compact scene rendering mode (litmus-1vws)

Add compact prop to SceneView: smaller font, tighter padding, max-height with fade-out gradient. Makes 19 themes fit in ~4 screens.

Summary of Changes

The scene-across-themes page now uses compact=true on SceneView, which uses smaller font, tighter padding, and max-height with fade-out gradient. Makes 19 themes scannable in a grid.