[Feature] Have `Alt+F: bindings` on the top right of the screen (when it fits)

I suggested people make edit replace nano as the default, and a complaint I got was that it it was too difficult to figure out how to view the bindings. I think this would solve that.

The issue does not name files or tests. Start by locating the bindings display and the top-right layout logic, then determine how available space is measured; the work is done when `Alt+F: bindings` appears at the top right only when it fits without disrupting the editor.

Written by the indexing model from the issue text.