Correct ADV History layout addressing

engine/Age.Engine/Vm/Frame.cs

@@ -1,9 +1,27 @@
 namespace Age.Engine.Vm;
+
+public enum VmAddressSpace
+{
+    Global,
+    LocalInteger,
+    LocalFloat,
+    LocalString,
+}
+
+public readonly record struct VmAddress(VmAddressSpace Space, int Address)
+{
+    public static VmAddress Global(int address) => new(VmAddressSpace.Global, address);
+    public static VmAddress LocalInteger(int address) => new(VmAddressSpace.LocalInteger, address);
+    public static VmAddress LocalFloat(int address) => new(VmAddressSpace.LocalFloat, address);
+    public static VmAddress LocalString(int address) => new(VmAddressSpace.LocalString, address);
+    public VmAddress Offset(long offset) => new(Space, checked(Address + (int)offset));
+}
+
 public sealed class Frame
 {
     public Dictionary<int, long> I = new();   // local-int
     public Dictionary<int, long> F = new();   // local-float (raw)
     public Dictionary<int, string> S = new(); // local-string
-    public Dictionary<int, long> P = new();   // local-ptr (holds a global address)
-    public Dictionary<int, long> SP = new();  // local-string-ptr (holds a global-string address)
+    public Dictionary<int, VmAddress> P = new();  // local-ptr (retains local/global address domain)
+    public Dictionary<int, VmAddress> SP = new(); // local-string-ptr (same, for the string banks)
 }