SpriteSheetUVNode: Transform to TSL function and fix countNode access.

[gayanMatch]

Fixed #32688

Description

This PR refactors SpriteSheetUVNode from a class-based Node to a modern TSL Fn function, as requested by the reviewer.

Changes:

• Removed the SpriteSheetUVNode class entirely
• Replaced with a pure TSL Fn function implementation of spritesheetUV()
• Updated imports to use Fn instead of nodeProxy and removed unused Node import
• Preserved all existing functionality and logic - the UV calculation remains identical
• Maintained backward compatibility - the public API (spritesheetUV()) is unchanged

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Contribution by Gittensor, see my contribution statistics at https://gittensor.io/miners/details?githubId=132382032

[sunag]

Some aditional taks:

• Rename the file SpriteSheetUVNode.js -> SpriteSheetUV.js and update the TSL.js reference
• Remove the export SpriteSheetUVNode of Nodes.js file

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	355.36 84.47	355.36 84.47	+0 B +0 B
WebGPU	621.54 172.59	621.3 172.52	-244 B -70 B
WebGPU Nodes	620.15 172.35	619.9 172.28	-244 B -72 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	487.31 119.25	487.31 119.25	+0 B +0 B
WebGPU	692.53 187.85	692.53 187.85	+0 B +0 B
WebGPU Nodes	642.34 175.07	642.34 175.07	+0 B +0 B

[gayanMatch]

Some aditional taks:

• Rename the file SpriteSheetUVNode.js -> SpriteSheetUV.js and update the TSL.js reference
• Remove the export SpriteSheetUVNode of Nodes.js file

@sunag Fixed!