Improved HTMLTexture support.

[mrdoob]

Related issue: #31233

Description

• Fixed texElement2D API check to use the spec-correct texElementImage2D
• Added HTMLTexture support to the WebGL fallback backend (webgl-fallback/utils/WebGLTextureUtils.js)
• Centralized onpaint callback handling in common Textures.js for both WebGPU and WebGL fallback paths
• Added three-html-render polyfill fallback to both examples
• Fixed onpaint handler to only update textures whose elements actually changed (via event.changedElements)
• Fixed multiple HTMLTexture support — shared onpaint handler iterates over all registered textures
• Added HTMLTexture examples to the e2e exception list (requires HTML-in-Canvas API)
• Updated screenshots

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	364.99 86.71	365 86.71	+5 B +0 B
WebGPU	637.49 177.06	637.56 177.1	+74 B +37 B
WebGPU Nodes	635.61 176.77	635.68 176.8	+74 B +37 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	497.51 121.39	497.51 121.39	+5 B +1 B
WebGPU	709.24 191.88	709.32 191.9	+74 B +18 B
WebGPU Nodes	658.46 179.18	658.54 179.19	+74 B +17 B