feat(blocks): add ore block scaffolding (Coal, Iron, Gold, Diamond)

World/Blocks/CoalOreBlock.cs

@@ -0,0 +1,10 @@
+namespace VoxelEngine.World.Blocks;
+
+public sealed class CoalOreBlock : IBlock
+{
+    public ushort Id => 7;
+    public string Name => "Coal Ore";
+    public bool IsOpaque => true;
+    public bool IsSolid => true;
+    public TileCoord GetTextureTile(BlockFace face) => new(0, 0); // placeholder
+}