search and sign in buttons hidden on narrow display

Summary

If the browser window is very narrow then some crucial buttons in the top bar are no longer visible and key functionality becomes inaccessible.

This can easily happen on mobile devices which have limited screen sizes.

Downstream report: https://gitlab.gnome.org/Infrastructure/GitLab/issues/346

Steps to reproduce

Resize the browser to make it very narrow.

Example Project

Any. Even this project here.

What is the current bug behavior?

Buttons gradually disappear as things get narrow. At some point (...) appears to handle everything that goes missing. At some further point (...) gets pushed off screen.

What is the expected correct behavior?

(...) stays on screen even when things get very narrow.

(or some other mechanism shows up to access missing items)