Bug: occluding math equations

> If I have a card that contains an equation and I trigger cloze with ctrl+shift+c right “around” the equation, it leads to the equation disappearing and the close appearing in the wrong place.

> Steps to reproduce:
> Put a “Text (x^2) more text” into the Text input field of a cloze card.
> Switch focus away and back to the window, so that the latex is rendered.
> Place your cursor inside the equation.
> click the left arrow until you get out of the equation editor
> Press ctrl+shift+right_arrow to select the entire equation.
> Press ctrl+shift+c to occlude.
>

Originally reported on https://forums.ankiweb.net/t/bug-ocluding-math-equations/42685

Reproduce the issue in a cloze card using the provided text and keyboard sequence, after switching focus so the LaTeX is rendered. Inspect the cloze editor's handling of a selected equation and compare the result with normal text occlusion. Done means the equation remains visible and the occlusion appears in the selected location.

Written by the indexing model from the issue text.