[v11] webgpu/BlurPass is still the WebGL implementation and imports from legacy

Problem

src/webgpu/Materials/BlurPass/BlurPass.tsx is not a WebGPU implementation. Its own first line says so:

//* TODO: Convert GLSL shaders to TSL for WebGPU ==============================

import { Mesh, BufferGeometry, ..., WebGLRenderTarget, WebGLRenderer, ... } from '#three'
import { ConvolutionMaterial } from '@legacy/Materials/ConvolutionMaterial'

Two problems:

1. It imports the legacy GLSL ConvolutionMaterial — a ShaderMaterial — from the legacy tree. This is the only webgpu → legacy import in the codebase.

2. It imports WebGLRenderer, which three/webgpu does not export. Verified:

   复制

   WebGLRenderer       ** NOT EXPORTED **
   WebGLRenderTarget   exported
   RenderTarget        exported

That is the same shape as #2764. It is not currently breaking anything only because it is deliberately excluded from the barrel — src/webgpu/Materials/index.ts has //export * from './BlurPass', and the built webgpu/index.mjs contains zero references to it. That call was correct.

Why this matters beyond BlurPass

It explains #2661. The legacy MeshReflectorMaterial blurs its reflection with this pass:

'defines-USE_BLUR': hasBlur ? '' : undefined,   // legacy :181
if (hasBlur) blurpass.render(gl, fbo1, fbo2)    // legacy :223

The WebGPU MeshReflectorMaterial computes hasBlur at line 83 and never uses it — because there is no usable WebGPU BlurPass to call. So blur is inert on WebGPU, which is consistent with the "wrong reflections" report.

Why this is agent-ok

A TSL ConvolutionMaterial already exists right next to it, at src/webgpu/Materials/ConvolutionMaterial/, and is exported. The conversion is largely:

• swap @legacy/Materials/ConvolutionMaterial → ./ConvolutionMaterial
• WebGLRenderTarget → RenderTarget (exported by three/webgpu)
• WebGLRenderer → the R3FRenderer union, or drop the annotation — see getMaxAnisotropy() in src/utils/generic.ts for the narrowing pattern
• re-enable the barrel export

Visual verification needs a GPU, so the result wants human review even though the change does not.

Acceptance

• src/webgpu/Materials/BlurPass uses the TSL ConvolutionMaterial and no legacy import.
• It is exported from /webgpu and yarn test:bundles still passes.
• MeshReflectorMaterial's hasBlur is wired to it, and blur visibly changes the reflection (#2661).