WebGPUUtils: Ensure sample count is valid

[ycw]

Description

This PR ensures sample count used by Texture(sampleCount) or Pipeline(multisample.count) must be 1 or 4

Defined at:

• https://gpuweb.github.io/gpuweb/#abstract-opdef-validating-gputexturedescriptor

• https://gpuweb.github.io/gpuweb/#abstract-opdef-validating-gpumultisamplestate

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	337.69 78.76	337.69 78.76	+0 B +0 B
WebGPU	557.35 154.34	557.29 154.31	-60 B -23 B
WebGPU Nodes	556.27 154.12	556.21 154.09	-60 B -23 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	468.91 113.45	468.91 113.45	+0 B +0 B
WebGPU	632.98 171.34	632.91 171.31	-60 B -22 B
WebGPU Nodes	588.11 160.69	588.05 160.67	-60 B -22 B