Transpiler native record support for VM types (Step 5.5 unblock)

- Add VmFrame/VmMachine types to sx_types.ml (alongside CekState/CekFrame)
- Add VmFrame/VmMachine value variants to the value sum type
- Extend get_val in sx_runtime.ml to dispatch on VmFrame/VmMachine fields
- Extend sx_dict_set_b for VmFrame/VmMachine field mutation
- Extend transpiler ml-emit-dict-native to detect VM dict patterns
  and emit native OCaml record construction (same mechanism as CekState)
- Retranspile evaluator — no diff (transpiler extension is additive)
- Update bootstrap_vm.py output location

The transpiler now handles 4 native record types:
  CekState (5 fields), CekFrame (10 fields),
  VmFrame (4 fields), VmMachine (5 fields)

Full VM replacement (sx_vm.ml → transpiled) still needs vm.sx
feature parity: JIT dispatch, CEK fallback, suspension handling.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/transpiler.sx

@@ -573,22 +573,52 @@
                 (ef "first-render")
                 :else "Nil")
               " })"))
-          (str
-            "(let _d = Hashtbl.create "
-            (str (round (len items)))
-            " in "
-            (join
-              "; "
-              (map
-                (fn
-                  (k)
-                  (str
-                    "Hashtbl.replace _d "
-                    (ml-quote-string k)
-                    " "
-                    (ml-expr-inner (get d k) set-vars)))
-                items))
-            "; Dict _d)"))))))
+          (if
+            (and
+              (some (fn (k) (= k "ip")) items)
+              (some (fn (k) (= k "closure")) items)
+              (some (fn (k) (= k "base")) items))
+            (str
+              "(VmFrame { vf_closure = (match "
+              (ml-expr-inner (get d "closure") set-vars)
+              " with VmClosure c -> c | _ -> failwith \"vf_closure\")"
+              "; vf_ip = val_to_int "
+              (ml-expr-inner (get d "ip") set-vars)
+              "; vf_base = val_to_int "
+              (ml-expr-inner (get d "base") set-vars)
+              "; vf_local_cells = Hashtbl.create 4 })")
+            (if
+              (and
+                (some (fn (k) (= k "sp")) items)
+                (some (fn (k) (= k "stack")) items)
+                (some (fn (k) (= k "globals")) items))
+              (str
+                "(VmMachine { vm_stack = (match "
+                (ml-expr-inner (get d "stack") set-vars)
+                " with List _ -> Array.make 4096 Nil | _ -> Array.make 4096 Nil)"
+                "; vm_sp = val_to_int "
+                (ml-expr-inner (get d "sp") set-vars)
+                "; vm_frames = []"
+                "; vm_globals = (match "
+                (ml-expr-inner (get d "globals") set-vars)
+                " with Dict d -> d | _ -> Hashtbl.create 0)"
+                "; vm_pending_cek = None })")
+              (str
+                "(let _d = Hashtbl.create "
+                (str (round (len items)))
+                " in "
+                (join
+                  "; "
+                  (map
+                    (fn
+                      (k)
+                      (str
+                        "Hashtbl.replace _d "
+                        (ml-quote-string k)
+                        " "
+                        (ml-expr-inner (get d k) set-vars)))
+                    items))
+                "; Dict _d)"))))))))
 
 (define
   ml-emit-list