[BREAKING] Update gsplat component material API

[slimbuck]

Further to #7734, this PR updates the gsplat component material API.

We drop materialOptions property (which indirectly reconfigured the material) in favour of exposing the material instance directly. This matches the render and model components.

The gsplat component will create a default material if none is provided at construction, but this can then be overridden at will.

Notes

• the internal function GSplatInstance.configureMaterial accepts a ShaderMaterial instance and configures it with the gsplat data. This function could be useful as public API, but we must still decide how to expose it.
• cloning a gsplat component doesn't clone the material. if it did, then the sort texture would be shared.

[Copilot]

Pull Request Overview

This PR refactors the GSplat material API to expose and configure material instances directly, replacing the old materialOptions pattern and unifying behavior across resource, instance, and component layers.

• Replace createMaterial methods with a configureMaterial(material) API on resource classes
• Update GSplatInstance to accept a provided ShaderMaterial (or build a default one), add a getter/setter for material, and centralize material configuration
• Refactor GSplatComponent to use a material property (stored in _materialStore) instead of materialOptions, and apply overrides at instance creation

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/scene/gsplat/gsplat-sogs-resource.js	Renamed createMaterial to configureMaterial
src/scene/gsplat/gsplat-resource.js	Renamed createMaterial to configureMaterial
src/scene/gsplat/gsplat-compressed-resource.js	Renamed createMaterial to configureMaterial
src/scene/gsplat/gsplat-resource-base.js	Added empty base stubs for configureMaterial and evalTextureSize
src/scene/gsplat/gsplat-instance.js	Overhauled to use provided ShaderMaterial, added material getter/setter and configureMaterial
src/framework/components/gsplat/component.js	Switched from materialOptions to storing/applying ShaderMaterial directly
src/platform/graphics/webgpu/...	Guarded WebGPU calls on window.navigator and added optional chaining

Comments suppressed due to low confidence (1)

src/scene/gsplat/gsplat-instance.js:127

• [nitpick] There’s no existing unit test covering the new material setter or the path where an external ShaderMaterial is provided. Adding tests would ensure correct assignment, mesh update, and avoid regressions.

set material(value) {

[mvaligursky]

The PR should probably be maked as [BREAKING]?

[mvaligursky]

Also please update the examples to work, I suspect some do not.