Function slice_steps 

pub fn slice_steps(
    steps: Vec<Step>,
    range: &StepRange,
    after_ms: Option<u64>,
    before_ms: Option<u64>,
) -> Vec<Step>

Slice the steps by index range and optional time bounds. Time bounds are offsets in milliseconds from the session’s first step’s timestamp. When no step carries a timestamp, time filters are silently skipped (and the caller gets a stderr warning from warn_if_time_filter_ignored — kept out here so this function stays pure).