The renderer applies every ancestor's transform, so a scaled null above a
camera already carries the camera's children. A Scale key with one shared
ease gets a separate Z ease before its speed is scaled.
Position speeds stretch with the path's direction at each key and Scale's Z
speed with the factor, so the ease keeps its shape. A 3D layer under a 2D
parent scales its own Z only when no 3D ancestor's Scale already carries it.
A 2D parent's Scale carries no depth, so its 3D children scale their own Z.
Percentage guides keep their percent exactly instead of drifting by rounding.
Tests now check the specific errors and cover a layer parented to a camera.
Like After Effects' File > Scripts > Scale Composition.jsx: a factor, or a new
width or height that keeps the aspect ratio, in one undo step. Layers whose
parent has a Scale follow that parent; nested precomps and expressions are
left as they are. No dialog yet.
Refs #2208
Marco Arnulfo