MaterialNode: Fix dashOffset with LineDashedMaterial.

[Mugen87]

Fixed #31006.

Description

LineDashedNodeMaterial is the node variant of LineDashedMaterial. The node version supports a property dashOffset which does exist for LineDashedMaterial. To make the TSL material property materialLineDashOffset compatible with LineDashedMaterial, MaterialNode must check for the existence of dashOffset before creating a uniform node. Otherwise a constant is used.

The PR also applies a minor fix to webgpu_lines_fat_wireframe which ensures the right dash scale property name is used.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.33 78.33	336.33 78.33	+0 B +0 B
WebGPU	547.49 151.78	547.56 151.81	+70 B +38 B
WebGPU Nodes	546.84 151.62	546.91 151.66	+70 B +40 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	465.78 112.28	465.78 112.28	+0 B +0 B
WebGPU	622.34 168.36	622.41 168.39	+70 B +29 B
WebGPU Nodes	577.22 157.63	577.29 157.65	+70 B +21 B