SX bytecode VM executing: compile → run → correct results

End-to-end pipeline working:
  Python compiler.sx → bytecode → OCaml VM → result

Verified: (+ (* 3 4) 2) → 14 ✓
          (+ 0 1 2 ... 49) → 1225 ✓

Benchmark (500 iterations, 50 additions each):
  CEK machine: 327ms
  Bytecode VM: 145ms
  Speedup: 2.2x

VM handles: constants, local variables, global variables,
primitive calls, jumps, conditionals, closures (via NativeFn
wrapper), define, return.

Protocol: (vm-exec {:bytecode (...) :constants (...)})
  - Compiler outputs clean format (no internal index dict)
  - VM converts bytecode list to int array, constants to value array
  - Stack-based execution with direct opcode dispatch

The 2.2x speedup is for pure arithmetic. For aser (the real
target), the speedup will be larger because aser involves:
- String building (no CEK frame allocation in VM)
- Map/filter iterations (no frame-per-iteration in VM)
- Closure calls (no thunk/trampoline in VM)

Next: compile and run the aser adapter on the VM.

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

spec/compiler.sx

@@ -375,7 +375,7 @@
       ;; Add code object to parent constant pool
       (let ((code {:arity (len (get fn-scope "locals"))
                    :bytecode (get fn-em "bytecode")
-                   :pool (get fn-em "pool")
+                   :constants (get (get fn-em "pool") "entries")
                    :upvalues (get fn-scope "upvalues")})
             (code-idx (pool-add (get em "pool") code)))
         (emit-op em 51)  ;; OP_CLOSURE
@@ -466,7 +466,7 @@
       (compile-expr em expr scope false)
       (emit-op em 50)  ;; OP_RETURN
       {:bytecode (get em "bytecode")
-       :pool     (get em "pool")})))
+       :constants (get (get em "pool") "entries")})))
 
 (define compile-module
   (fn (exprs)
@@ -481,4 +481,4 @@
       (compile-expr em (last exprs) scope false)
       (emit-op em 50)  ;; OP_RETURN
       {:bytecode (get em "bytecode")
-       :pool     (get em "pool")})))
+       :constants (get (get em "pool") "entries")})))