It can create a kind of phantom-focus state where the textarea
is focused but you can't type into it.

Issue #3041

I.e. when the cursor is directly in the editor's top node or outside of a line's
<pre> node.

So that the contenteditable input style doesn't look silly
on desktop.

It apparently believes that if the editor's nodes are directly next to
each other without margin, the user needs a magnifying glass to pick
a cursor position.

Still doesn't work properly

Simple things work.

Add a dummy ContentEditableInput

Closes #3093

Issue #3095

Issue #3089

Both to the annotateScrollbar and to the editor itself.