Move syntax models to own folder

libs/UIX.Asm/Models/Import.cs

@@ -0,0 +1,6 @@
+namespace Microsoft.Iris.Asm.Models;
+
+public record NamespaceImport(string Uri, string Name) : IImport
+{
+    public override string ToString() => $".import-ns {Uri} as {Name}";
+}

libs/UIX.Asm/Models/SyntaxModels.cs

@@ -0,0 +1,31 @@
+using Microsoft.Iris.Markup;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Microsoft.Iris.Asm.Models;
+
+public interface IBodyItem { }
+public interface IImport { }
+
+public record Instruction(string Mnemonic, IEnumerable<Operand> Operands) : IBodyItem
+{
+    public OpCode OpCode => LexerMaps.MnemonicToOpCode(Mnemonic);
+    public OperationType? OperationType => LexerMaps.TryOperationMnemonicToType(Mnemonic);
+
+    public override string ToString() => $"{Mnemonic} {string.Join(", ", Operands)}";
+}
+
+public record Label(string Name) : IBodyItem
+{
+    public override string ToString() => $"{Name}:";
+}
+
+public record Operand(object Value, string Content = null)
+{
+    public override string ToString() => Content ?? Value.ToString();
+}
+
+public record Program(IEnumerable<IImport> Imports, IEnumerable<IBodyItem> Body)
+{
+    public override string ToString() => string.Join("\r\n", Imports.Select(i => i.ToString()).Concat(Body.Select(b => b.ToString())));
+}