Summary:
On narrow screens, there wasn't enough room in the top bar to see the
text you were typing into the search input. To make more room, items to
the left of the search input are now hidden while search is open; the document
title is hidden on narrow screens, and the undo and redo buttons are always
hidden.
Test Plan: Manual.
Reviewers: JakubSerafin
Reviewed By: JakubSerafin
Subscribers: JakubSerafin
Differential Revision: https://phab.getgrist.com/D4187