feat: render 2 rotating cubes side by side

- Push constant changed from float angle (4B) to mat4 model (64B)
- Two draw calls with different model matrices (x=-1.5 and x=+1.5)
- Both cubes rotate around Y axis at 0.2 rad/s
- 0 validation errors

src/Engine.Graphics.Vulkan/Shaders/triangle.vert

@@ -10,18 +10,11 @@ layout(row_major, set = 0, binding = 0) uniform CameraUBO {
     mat4 vp;
 };
 
-layout(push_constant) uniform PC {
-    float angle;
+layout(row_major, push_constant) uniform PC {
+    mat4 model;
 } pc;
 
 void main() {
-    float c = cos(pc.angle);
-    float s = sin(pc.angle);
-    vec3 rotated = vec3(
-        inPosition.x * c - inPosition.z * s,
-        inPosition.y,
-        inPosition.x * s + inPosition.z * c
-    );
-    gl_Position = vp * vec4(rotated, 1.0);
+    gl_Position = vp * pc.model * vec4(inPosition, 1.0);
     fragColor = inColor;
 }

src/Engine.Graphics.Vulkan/VulkanPipeline.cs

@@ -154,7 +154,7 @@ internal sealed unsafe class VulkanPipeline : IDisposable
             {
                 stageFlags = VkShaderStageFlags.Vertex,
                 offset = 0,
-                size = 4,
+                size = 64,
             };
 
             var descLayout = DescriptorSetLayout;

src/Engine.Graphics.Vulkan/VulkanRenderer.cs

@@ -188,9 +188,15 @@ internal sealed unsafe class VulkanRenderer : IRenderer, Engine.Graphics.IScreen
 
         Vk.vkCmdBindIndexBuffer(cmd, _indexBuffer.Buffer, 0, 1);
 
-        float angle = _totalTime * 0.2f;
-        Vk.vkCmdPushConstants(cmd, _pipeline.PipelineLayout, VkShaderStageFlags.Vertex, 0, 4, &angle);
+        var angle = _totalTime * 0.2f;
+        var rot = Matrix4x4.CreateRotationY(angle);
 
+        var model1 = Matrix4x4.CreateTranslation(-1.5f, 0, 0) * rot;
+        Vk.vkCmdPushConstants(cmd, _pipeline.PipelineLayout, VkShaderStageFlags.Vertex, 0, 64, &model1);
+        Vk.vkCmdDrawIndexed(cmd, _indexCount, 1, 0, 0, 0);
+
+        var model2 = Matrix4x4.CreateTranslation(1.5f, 0, 0) * rot;
+        Vk.vkCmdPushConstants(cmd, _pipeline.PipelineLayout, VkShaderStageFlags.Vertex, 0, 64, &model2);
         Vk.vkCmdDrawIndexed(cmd, _indexCount, 1, 0, 0, 0);
 
         Vk.vkCmdEndRendering(cmd);