Restore behavioral render preset override coverage

tools/d4r_render_presets.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <cstdlib>
+
+// Platform-specific environment reads stay in the caller. SR and RR deliberately
+// use separate settings, even when both are configured for the same feature call.
+inline constexpr const char* d4r_render_preset_variable(bool rayReconstruction)
+{
+    return rayReconstruction ? "D4R_RR_PRESET" : "D4R_DLSS_PRESET";
+}
+
+// An absent/empty override leaves every game-selected quality preset unchanged.
+// An explicit zero is an override too: it requests NGX's default preset.
+struct D4rRenderPresetOverride
+{
+    bool enabled;
+    unsigned int value;
+
+    void apply(unsigned int (&presets)[6]) const
+    {
+        if (enabled)
+            for (unsigned int& preset : presets)
+                preset = value;
+    }
+};
+
+inline D4rRenderPresetOverride d4r_parse_render_preset_override(const char* overrideValue)
+{
+    if (overrideValue == nullptr || *overrideValue == '\0')
+        return {false, 0};
+    return {true, static_cast<unsigned int>(std::strtoul(overrideValue, nullptr, 0))};
+}