AnimationAction: Preserve interpolant settings on action creation.

[gigajuad]

Fixed #33032

Description

When using InterpolateBezier with the animation system, the BezierInterpolant ends up doing linear interpolation because the AnimationAction constructor overwrites interpolant.settings with a shared ending-behavior object, wiping out the inTangents and outTangents data.

The interpolant is created correctly with tangent data, but by the time it runs, that data is gone.

To fix, the AnimationAction constructor is slightly modified to append the track.settings instead of replacing it.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	359.15 85.24	359.15 85.24	+0 B +0 B
WebGPU	623.55 173.47	623.55 173.47	+0 B +0 B
WebGPU Nodes	622.13 173.21	622.13 173.21	+0 B +0 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	490.87 119.65	490.87 119.65	+0 B +0 B
WebGPU	697.03 188.44	697.03 188.44	+0 B +0 B
WebGPU Nodes	646.24 175.82	646.24 175.82	+0 B +0 B