Implement post-processing pipeline #40

Implement a post-processing pipeline for the Scene View and final output.

Parent Issue

Part of the 3D scene pipeline improvements.

Current State

No post-processing exists. The render pipeline outputs directly to the swapchain/framebuffer without any intermediate passes; standardShader.frag applies a fixed Reinhard tonemap and gamma inline, which should move into this pipeline.

Tasks:

• Implement render-to-texture infrastructure (intermediate framebuffer)
• Create a post-processing effect system (chain of effects applied in order)
• Implement Bloom (Gaussian blur + additive blend)
• Implement Tonemapping (ACES, Reinhard, or Unity URP tonemapper)
• Implement FXAA or TAA anti-aliasing
• Implement SSAO (Screen-Space Ambient Occlusion)
• Add post-processing volume/stack component for per-scene configuration
• Create a post-processing editor panel in Studio

Acceptance Criteria:

• Post-processing effects can be enabled/disabled and ordered.
• Bloom, tonemapping, and anti-aliasing are functional.
• Effects are configurable per-scene via a component.
• Performance impact is measurable and documented.

Related:

• Implement shadow mapping for lights #39 (RHI — render target abstraction)