WebGPURenderer: Fix viewport/scissor after copyFramebufferToTexture()

[sunag]

Description

Update viewport/scissor after copyFramebufferToTexture() is called.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	339.14 78.99	339.14 78.99	+0 B +0 B
WebGPU	483.57 134.16	483.72 134.2	+144 B +37 B
WebGPU Nodes	483.04 134.06	483.18 134.1	+144 B +40 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	464.62 111.98	464.62 111.98	+0 B +0 B
WebGPU	552.7 149.51	552.85 149.55	+144 B +42 B
WebGPU Nodes	508.58 139.23	508.73 139.27	+144 B +41 B