Function steps 

pub fn steps(
    op: &ElementOp,
    gate: &Gate,
    settable: bool,
    char_count: Option<i64>,
    explicit_tier: Option<&str>,
) -> Result<Vec<Step>, ElementError>

Build the steps that run after settable and character-count reads.

explicit_tier is the raw value the caller passed for --tier. None or empty means “auto”: the accessibility value is used when the element advertises it as settable; otherwise the keystroke fallback runs. A non-empty value (e.g. "event") forces the keystroke path because set_value REPLACES the field contents and the caller explicitly asked for keystroke input.