[OopyDoopy]

Summary

• Add Densha Attack post-processing shader overrides for color vignette, speedlines, and an additional post-effect pass.
• Add shared LUT encode/decode helpers in postfx.hlsli for the current processing path.
• Preserve the existing Vanilla/0 behavior while routing custom tone-map output through the shared processing path.

Verification

• Confirmed the four intended files are committed and the working tree is clean.
• Shader/runtime verification remains for game-side testing.

RenoDX review checklist

• PR scope and commits are tidy: Pass
• Defaults preserve the original/vanilla look: Needs runtime verification
• Preset Off/reset and Vanilla/0 behavior are clear: Pass
• No final-frame inverse tonemapping: Pass
• Tonemap/LUT signal and domain handling: Needs runtime verification
• Output mode and swapchain handling: N/A