feat(terrain): add animated fractal tree with hierarchical transforms

feat(terrain): add animated fractal tree with hierarchical transforms

Implement recursive branching structure using AbstractCompositeShape with
Transform inheritance. Each branch has its own transform (position + rotation)
and recursively creates 3 sub-branches at 120-degree spacing, up to 5 levels
deep. Branches animate with sine-wave wobble using beforeTransformHook, where
parent motion cascades to children via TransformStack.

Add FrameListener to TerrainDemo for continuous animation updates. Make galaxy
generation deterministic with fixed rotation angles for reproducible demo
screenshots. Reorganize demo launcher with improved grouping.

Expand documentation with detailed descriptions for point cloud galaxy, raining
numbers, procedural terrain, and benchmark demos. Add responsive image
attributes and new screenshots.