rendering: formalize main light shadow params

engine/include/XCEngine/Rendering/FrameData/RenderSceneData.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <XCEngine/Core/Math/Vector2.h>
 #include <XCEngine/Core/Math/Vector3.h>
 #include <XCEngine/Core/Math/Vector4.h>
 #include <XCEngine/Rendering/FrameData/RenderCameraData.h>
@@ -50,11 +51,32 @@ struct RenderAdditionalLightData {
     float spotAngle = 0.0f;
 };
 
+struct RenderDirectionalShadowMapMetrics {
+    Math::Vector2 inverseMapSize = Math::Vector2::Zero();
+    float worldTexelSize = 0.0f;
+    float padding = 0.0f;
+};
+
+static_assert(
+    sizeof(RenderDirectionalShadowMapMetrics) == sizeof(float) * 4u,
+    "RenderDirectionalShadowMapMetrics must stay float4-sized for GPU constant layout");
+
+struct RenderDirectionalShadowSamplingData {
+    float enabled = 0.0f;
+    float receiverDepthBias = 0.0f;
+    float normalBiasScale = 0.0f;
+    float shadowStrength = 0.0f;
+};
+
+static_assert(
+    sizeof(RenderDirectionalShadowSamplingData) == sizeof(float) * 4u,
+    "RenderDirectionalShadowSamplingData must stay float4-sized for GPU constant layout");
+
 struct RenderDirectionalShadowData {
     bool enabled = false;
     Math::Matrix4x4 viewProjection = Math::Matrix4x4::Identity();
-    Math::Vector4 shadowParams = Math::Vector4::Zero();
-    Math::Vector4 shadowOptions = Math::Vector4::Zero();
+    RenderDirectionalShadowMapMetrics mapMetrics = {};
+    RenderDirectionalShadowSamplingData sampling = {};
     RHI::RHIResourceView* shadowMap = nullptr;
 
     bool IsValid() const {

engine/include/XCEngine/Rendering/Pipelines/BuiltinForwardPipeline.h

@@ -91,8 +91,8 @@ private:
 
     struct ShadowReceiverConstants {
         Math::Matrix4x4 worldToShadow = Math::Matrix4x4::Identity();
-        Math::Vector4 shadowBiasAndTexelSize = Math::Vector4::Zero();
-        Math::Vector4 shadowOptions = Math::Vector4::Zero();
+        RenderDirectionalShadowMapMetrics shadowMapMetrics = {};
+        RenderDirectionalShadowSamplingData shadowSampling = {};
     };
 
     struct SkyboxConstants {

engine/include/XCEngine/Rendering/Planning/SceneRenderRequestPlanner.h

@@ -12,6 +12,9 @@ class Scene;
 
 namespace Rendering {
 
+// Planning-only knobs for fitting the single main-light shadow camera to the
+// current view. Receiver-side bias/filtering parameters live in runtime shadow
+// data and are not configured here.
 struct DirectionalShadowPlanningSettings {
     uint32_t mapDimension = 1024u;
     float minFocusDistance = 5.0f;