Add 3D pixel-art render style (pixelation + depth/normal outlines)

Full-screen URP post effect on the active PC renderer that pixelates the
scene to a fixed low-res grid and draws depth + normal edge-detection
outlines, with color posterization and tone controls, for a stylized
"3D pixel art" look. Runs via Unity's built-in Full Screen Pass feature
(no custom C#); reads camera depth/normals so it applies to DOTS entities
and GameObjects identically.

- PixelOutline.shader/.mat: pixel-snap fill + gamma-space posterize +
  brightness/contrast/saturation + depth/normal outlines. Normal
  threshold tuned high so outlines don't flood small characters.
- PC_Renderer.asset: FullScreenPassRendererFeature (Depth|Normal, after
  post-processing).
- PostFX_Daylight.asset: tonemapping ACES -> Neutral (poppier color).
- Game.unity: brighter base atmosphere (ambient + fog pushed back) and a
  stronger directional key light so the fill reads under the effect.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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