LightShadow: Support Reversed Depth

[WestLangley]

Previously, the shadow matrix mapped z to [ 0.5, 1 ] instead of [ 0, 1 ] when a reversed-depth projection matrix was used.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	338.22 78.88	338.22 78.88	+0 B +0 B
WebGPU	560.72 155.17	560.72 155.17	+0 B +0 B
WebGPU Nodes	559.64 154.96	559.64 154.96	+0 B +0 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	469.49 113.56	469.49 113.56	+0 B +0 B
WebGPU	635.72 172.04	635.78 172.05	+59 B +13 B
WebGPU Nodes	590.37 161.29	590.43 161.3	+59 B +16 B