- Machine.h:create/run_cycle + 可观察性(step/pc/fn_id/cycle_count/call_depth/data/reg)
- Fault:None/CycleLimit/StackOverflow/BadOp/BadSlot/BadConst
- 帧 { fn_id, regs[nregs], ret_pc, ret_fn_id },调用栈深度 64,MAIN 帧跨周期保留
- ctu_prev_ 预留(步骤 4);exec_one/do_call/do_ret/do_cal 桩