MR "Your review" button covers MR content on narrow viewports

Summary

The "Your review" button in the MR tab overlay gets squeezed down over the MR content when the browser is somewhat narrow.

Steps to reproduce

1. Visit MR with "Your review" button.
2. Adjust the browser width until the button moves into the wrong position.

See screenshot.

What is the current bug behavior?

The "Your review" button overlaps the MR content area when viewport width is insufficient to fit all header controls.

What is the expected correct behavior?

All header controls should remain visible without overlapping the main content, or wrap responsively.