Reduces vertex maximum stride to 16

https://wikis.khronos.org/opengl/Vertex_Specification_Best_Practices

> The alignment of any attribute's data should be no less than 4 bytes.

But to make it a bit safer for older drivers we prefer to use 16 bytes
alignment (vec4) for now to match std140.

binaries/data/mods/mod/shaders/glsl/compute_skinning.cs

@@ -26,7 +26,6 @@ struct Vertex
 	vec4 tangent;
 	vec4 normal;
 	vec4 position;
-	vec4 padding;
 };
 
 STORAGE_BUFFER(0) restrict readonly buffer InputVertices

source/renderer/GPUSkinnedModelRenderer.cpp

@@ -62,7 +62,7 @@ namespace
 //
 // Created on a model load and read by a compute shader for each frame where
 // the model is visible.
-//  InputVertex(size/stride=64):
+//  InputVertex(size/stride=48):
 //   vec4/CVector4D tangent (offset=0)
 //   vec3/CVector3D normal (offset=16)
 //   vec3/CVector3D position (offset=32)
@@ -251,7 +251,7 @@ ModelDefRData::ModelDefRData(const CModelDefPtr& modelDef)
 		m_UVArray.FreeBackingStore();
 	}
 
-	ENSURE(m_Array.GetStride() == INPUT_VERTEX_ATTRIBUTE_ALIGNMENT * 4);
+	ENSURE(m_Array.GetStride() == INPUT_VERTEX_ATTRIBUTE_ALIGNMENT * 3);
 	ENSURE(m_Position.offset == INPUT_VERTEX_POSITION_OFFSET);
 	ENSURE(m_Normal.offset == INPUT_VERTEX_NORMAL_OFFSET);
 	ENSURE(m_Tangent.offset == INPUT_VERTEX_TANGENT_OFFSET);

source/renderer/VertexArray.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2025 Wildfire Games.
+/* Copyright (C) 2026 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -231,10 +231,8 @@ static uint32_t RoundStride(uint32_t stride)
 		return 4;
 	if (stride <= 8)
 		return 8;
-	if (stride <= 16)
-		return 16;
 
-	return Align<32>(stride);
+	return Align<16>(stride);
 }
 
 // Re-layout by assigning offsets on a first-come first-serve basis,