chroma min/max amb mostreig bilinear subpíxel

source/core/rendering/sdl3gpu/sdl3gpu_shader.hpp

@@ -15,7 +15,7 @@
 struct PostFXUniforms {
     // vec4 #0
     float vignette_strength;
-    float chroma_strength;
+    float chroma_min;
     float scanline_strength;
     float screen_height;
     // vec4 #1
@@ -27,7 +27,7 @@ struct PostFXUniforms {
     float pixel_scale;
     float time;
     float flicker;
-    float pad2;
+    float chroma_max;
     // vec4 #3 — paràmetres de scanlines exposats al preset YAML
     float scan_dark_ratio;
     float scan_dark_floor;
@@ -92,7 +92,7 @@ namespace Rendering {
 
         PostFXUniforms uniforms_{
             .vignette_strength = 0.0F,
-            .chroma_strength = 0.0F,
+            .chroma_min = 0.0F,
             .scanline_strength = 0.0F,
             .screen_height = 0.0F,
             .mask_strength = 0.0F,
@@ -102,7 +102,7 @@ namespace Rendering {
             .pixel_scale = 1.0F,
             .time = 0.0F,
             .flicker = 0.0F,
-            .pad2 = 0.0F,
+            .chroma_max = 0.0F,
             // Defaults canònics: 2/3 brillant + 1/3 fosca, brillantor 42%, suavitzat complet (1 px físic).
             .scan_dark_ratio = 0.333F,
             .scan_dark_floor = 0.42F,