Module rendering/post-processing/post-processing-manager

Post-processing pipeline manager.

Three-stage pipeline:

1. Scene render → HDR HalfFloat target (with optional MSAA + SSAA)
2. Bloom pyramid → bloom texture (see BloomChain)
3. Mega-shader → LDR intermediate (see MegaShaderMaterial) ↳ samples HDR + bloom; applies chromatic lens distortion, detector noise, EOG, tone mapping, vignette in one pass.
4. Optional FXAA → backbuffer (see FxaaPass)

When FXAA is disabled, stage (3) writes directly to the backbuffer.