Function dispatch 

pub async fn dispatch(
    ctx: &DispatchContext,
    input: &str,
) -> Result<Option<DispatchOutput>, Never>

Parse, resolve, execute. Returns Ok(None) when the line is empty — callers should skip rendering in that case.

Errors

Never returns an error at this layer; engine failures become structured OutputLine::Alert entries so the operator sees them in context rather than as an unhandled result. The Result signature is kept because future commands (/rate, /plan, /execute) will need it.