/// Controller commands the host engine implements. hjkl-vim never mutates
/// the editor directly — it emits a command and the host (apps/hjkl) calls
/// the corresponding `Editor` method.
#[derive(Debug, Clone, PartialEq, Eq)]pubenumEngineCmd{
ReplaceChar { ch:char, count:usize},// Future variants land in chunks 2b–2e: FindChar, GotoMark, etc.
}