WGSL support for batching

[mvaligursky]

• batching chunk

[Copilot]

Pull Request Overview

This PR adds WGSL support for skin batching by introducing a new shader chunk and integrating it into the shader module system.

• Added a new WGSL shader chunk in skinBatch.js to compute bone matrices from a texture.
• Updated the shader chunks registry to include the new skinBatch shader.
• Made minor formatting adjustments in the WebGPU shader processor.

Reviewed Changes

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

File	Description
src/scene/shader-lib/chunks-wgsl/common/vert/skinBatch.js	Introduces the new WGSL shader chunk for skin batching.
src/scene/shader-lib/chunks-wgsl/chunks-wgsl.js	Integrates the new shader chunk into the shader registry.
src/platform/graphics/webgpu/webgpu-shader-processor-wgsl.js	Minor comment and formatting updates.

Comments suppressed due to low confidence (1)

src/scene/shader-lib/chunks-wgsl/common/vert/skinBatch.js:9

• [nitpick] Consider extracting the magic number '3' into a named constant (e.g., BONEMATRIX_ROW_COUNT) to clarify its purpose and improve maintainability.

let index: i32 = i32(indexFloat + 0.5) * 3;