Refactor VM to ExecFrame + tag emitted lines with source script (no behavior change)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

engine/Age.Engine/Model/Script.cs

@@ -1,6 +1,7 @@
 namespace Age.Engine.Model;
 public sealed class Script
 {
+    public string Name { get; init; } = "";
     public required ScriptHeader Header { get; init; }
     public required IReadOnlyList<Instruction> Instructions { get; init; }
     public required IReadOnlyDictionary<int, int> IndexByOffset { get; init; }