Implement tile-based shadow map system (TBSM)#75

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copilot/add-tile-based-shadowmap

Commits on Mar 7, 2026

Initial plan
Copilot
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Add tile-based shadow map system: TileShadowPass, shadow atlas, tile culling, shader support

Copilot
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bluesky013
committed
Fix atlas initial access flags and cleanup atlasInitialized field

Copilot
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bluesky013
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