fix: shadow map binding before draw + correct matrix transpose

- Use BeginShaderMode/EndShaderMode around DrawModelEx to keep shader active
- Bind shadow map on texture unit 1 BEFORE DrawModelEx (not after)
- Remove manual Matrix4x4.Transpose — SetShaderValueMatrix already handles
  row-major to column-major conversion via glUniformMatrix4fv(transpose=false)
- 66/66 tests, 145 FPS

src/Engine.Graphics.Raylib/RaylibRenderer.cs

@@ -133,10 +133,10 @@ public sealed class RaylibRenderer : IRenderer
             Raylib.BeginMode3D(shadowCamera);
 
             // Grab light view/proj matrices AFTER BeginMode3D (like official example)
-            // Raylib matrices are row-major, need to transpose for OpenGL (column-major)
-            var lv = Rlgl.GetMatrixModelview();
-            var lp = Rlgl.GetMatrixProjection();
-            lightViewProj = Matrix4x4.Transpose(lv * lp);
+            // SetShaderValueMatrix passes Matrix4x4 as-is to glUniformMatrix4fv(transpose=false)
+            // which interprets row-major System.Numerics as column-major = effectively transposed.
+            // So we just multiply directly (no manual transpose needed).
+            lightViewProj = Rlgl.GetMatrixModelview() * Rlgl.GetMatrixProjection();
 
             // Draw all shadow casters with the simple shadow shader
             world.Each((Entity e, ref EngineMesh mesh, ref EngineTransform transform) =>
@@ -198,22 +198,29 @@ public sealed class RaylibRenderer : IRenderer
                 var (axis, angle) = QuaternionToAxisAngle(rotation);
                 SetMaterialUniforms(material, model);
 
-                // Bind shadow map on Emission slot (texture unit 1) for each entity
+                // Bind shadow map on Emission slot (texture unit 1)
                 if (hasDirectionalLight && _shadowMapLoc >= 0)
                 {
                     unsafe { Raylib.SetMaterialTexture(ref model.Materials[0], MaterialMapIndex.Emission, shadowTex); }
                 }
 
-                Raylib.DrawModelEx(model, position, axis, angle * 180.0f / MathF.PI, scale, Color.White);
-
-                // Re-bind shadow map on unit 1 after DrawModelEx (it may have reset texture state)
+                // Use BeginShaderMode to lock our shader, then bind shadow map on unit 1
+                // BEFORE DrawModelEx so it's active during the draw
                 if (hasDirectionalLight && _shadowMapLoc >= 0)
                 {
+                    Raylib.BeginShaderMode(_shader);
                     Rlgl.ActiveTextureSlot(1);
                     Rlgl.EnableTexture(_shadowDepthTex);
                     Raylib.SetShaderValue(_shader, _shadowMapLoc, 1, ShaderUniformDataType.Int);
                     Rlgl.ActiveTextureSlot(0);
                 }
+
+                Raylib.DrawModelEx(model, position, axis, angle * 180.0f / MathF.PI, scale, Color.White);
+
+                if (hasDirectionalLight && _shadowMapLoc >= 0)
+                {
+                    Raylib.EndShaderMode();
+                }
             }
         });