feat(mesh-layers): port SimpleMeshLayer to WebGPU - #10485

Summary

Port SimpleMeshLayer to WebGPU as a small, independent change against master.

The existing WebGL vertex and fragment shaders, WebGL texture bindings, mesh transformations, and rendering behavior remain unchanged.

Changes

• Add a native WGSL SimpleMeshLayer shader covering instanced mesh transforms, geographic and Cartesian projections, smooth and flat Phong shading, texture sampling, opacity, picking, and highlighting.
• Extend the existing shader module with WebGPU uniform, texture, and sampler bindings while preserving its original GLSL uniform block.
• Preserve the existing WebGL texture sampler and use the native WebGPU texture binding only on WebGPU.
• Reuse the existing 100-Mini-Cooper mesh example as a dedicated website example with WebGL/WebGPU device tabs.
• Exclude the unrelated SolidPolygon shadow plane and shadow effects only in WebGPU mode until that separate layer is ported. WebGL continues to render the original complete example unchanged.
• Add a real GPU-backed test validating both textured and untextured mesh pipelines and checking WebGPU validation error scopes.
• Mark SimpleMeshLayer as WebGPU-supported in the developer guide.

Website example

WebGL compatibility

The existing GLSL shaders are unchanged. All existing SimpleMeshLayer golden images remain identical, including geographic, Cartesian, meter-offset, smooth-shading, and flat-shading cases.

Validation

• yarn build
• yarn lint
• yarn test-headless test/modules/mesh-layers
• yarn test-render test/render/test-cases/simple-mesh-layer.spec.ts — all 5 existing reference images pass.
• yarn test-website
• Actual WebGPU validation of textured and untextured mesh pipeline creation.
• Browser verification of the new dedicated example with WebGPU selected.