Replace the enhanced HDR with a port of RenoDX's tone mapper.

The game's ACES tonemap shader gets a GLSL function linked into its SPIR-V where it clamps each channel: the game's SDR result upgraded to the HDR range by luminance and mapped to the display with the RenoDRT curve, exposure, highlights, shadows, contrast, saturation, highlight saturation, blowout, flare and hue correction. The settings reach it as four vec4 the support buffer gains at 1440. The present encode is a port of the swap chain pass: gamma correction, gamut compression, the peak clamp and PQ. Without an HDR10 swapchain the shader gives the game's own SDR picture; native HDR is unchanged.

The menu offers Off, RenoDX and Native, with gamma correction, the tone mapper and its grading rows. The shader build compiles sources marked "keep functions" without optimisation so their functions survive for the splice.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/README-BuildKit.md

@@ -66,7 +66,7 @@ When it says `finished`, start `C:\Games\Ocarina\ocarina.exe`. You can delete `C
   it lasts at most about 20 seconds once the shaders are translated, and the remaining pipelines are built in the
   background while you play.
 - **Screen** in the menu has Upscaling (DLSS on NVIDIA RTX cards, FSR 3.1 on any card), Frame generation (FSR 3.1; it
-  needs DLSS or FSR 3.1 upscaling on), HDR (Native is the game's own HDR; turn HDR on in Windows first) and the
+  needs DLSS or FSR 3.1 upscaling on), HDR (the game's picture tone mapped to your display, with its own grading rows, or Native, the game's own HDR; turn HDR on in Windows first) and the
   resolution. Those marked "after restart" take effect when the game starts again.
 - DLSS needs `nvngx_dlss.dll` from NVIDIA beside `ocarina.exe` (the kit does not include it); FSR 3.1's
   `amd_fidelityfx_vk.dll` is copied there by the build.