feat(a1): VM core (operands+pointer semantics, handlers, emit-cap) + RECOVER

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

engine/Age.Engine/Vm/Frame.cs

@@ -0,0 +1,8 @@
+namespace Age.Engine.Vm;
+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)
+}