WebGPURenderer: Introduce compatibilityMode

[sunag]

Related issue: #30725

Description

Introduce WebGPU Compatibility Mode, this is the first of other complementary PRs that are in development. After the implementation of PMREM we were still generating mipmaps in CubeMaps, which is unnecessary since PMREM already does this in a 2d texture, this should save gpu memory and should help especially on mobile devices.

[Copilot]

Pull Request Overview

This PR introduces a WebGPU Compatibility Mode for the renderer and improves texture handling by eliminating unnecessary mipmap generation for CubeMaps. Key changes include:

• Adding an optional compatibilityMode parameter in the WebGPUBackend.
• Updating the texture creation logic in WebGPUTextureUtils to correctly handle cube textures.
• Removing the environment texture check from mipmap generation in the Textures module.

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
src/renderers/webgpu/utils/WebGPUTextureUtils.js	Adds a condition for cube textures, setting the textureBindingViewDimension appropriately.
src/renderers/webgpu/WebGPUBackend.js	Introduces the compatibilityMode parameter and passes a featureLevel option to the adapter.
src/renderers/common/Textures.js	Removes the environment texture check from the mipmap generation logic as PMREM now handles it.

Files not reviewed (1)

• examples/webgpu_loader_gltf.html: Language not supported

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.39 78.35	336.39 78.35	+0 B +0 B
WebGPU	540.64 149.78	540.78 149.8	+142 B +19 B
WebGPU Nodes	540.1 149.68	540.25 149.7	+142 B +20 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	465.37 112.21	465.37 112.21	+0 B +0 B
WebGPU	613.53 165.84	613.67 165.87	+142 B +28 B
WebGPU Nodes	568.52 155.25	568.66 155.28	+142 B +25 B