Function refuse_hold_without_preemption 

pub fn refuse_hold_without_preemption(
    program: &HappensBeforeProgram,
    path: &Path,
    reason: &str,
) -> Result<()>

Refuse a version-2 program on a run without a preemption timer, saying why (reason). A version-2 spec bounds every hold by max_hold_ns, charged in committed virtual time; without the timer a thread that spins without syscalls never ends its turn, committed time stops, and a hold could never be charged, so the run would hang instead of ending in HERMIT_HB_HOLD_BUDGET_EXCEEDED. Called before launch twice: for an explicit --max-timeslice disabled, and after argument validation, when the timer can also be lost because the host cannot arm it. A version-1 program has no budget and is never refused here.