Function draw 

fn draw(
    (cur_lnum, extmarks, opts): (String, Vec<Extmark>, Option<Opts>),
) -> Option<String>

Draws the status column for the current buffer.

Special cases:

• When buftype == "grug-far" returns a single space string to minimize visual noise in transient search buffers.

Rationale

Using Option<String> (instead of empty placeholder) allows caller-side distinction between an intentional blank status column (special buffer type) and an error acquiring required state.