Renderer: Added sync .compute() support

[sunag]

Related issue: #29503 (comment)

Description

I'm thinking about improving the computational geometry example with material.geometryNode to handle computation only when the object is rendered. Among some other benefits we can get like #29503 (comment) we will need synchronous computation to avoid race condition problem.

• Renderer: Added sync compute()
• ComputeNode: Use .onInit( fn ) instead of .onInit=fn
• Update examples

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	688.13 170.5	688.13 170.5	+0 B +0 B
WebGPU	807.25 217.46	807.5 217.49	+256 B +35 B
WebGPU Nodes	806.76 217.32	807.01 217.36	+256 B +35 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	462.85 111.78	462.85 111.78	+0 B +0 B
WebGPU	536.06 144.73	536.32 144.76	+256 B +30 B
WebGPU Nodes	492.14 134.46	492.4 134.49	+256 B +30 B