Adds opcode 112 (OP_PERFORM / IO suspension) to lib/vm.sx's vm-step
dispatch. The native sx_vm.ml already has this opcode — this brings
the SX spec into alignment.
Full VM transpilation deferred to Step 6 (define-record-type): the
dict-based state in vm.sx maps to get_val/sx_dict_set_b calls which
are ~5x slower than native record/array access in the hot loop.
define-record-type will let vm.sx use typed records that the
transpiler maps to OCaml records natively.
2598/2598 tests passing.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
giles
b6f304e91a