The header-right tray (02fa3f3) was reworked into a position:fixed
collapsible panel with a hamburger toggle, but the toggle button, its
JS, and CSS were later reverted on master while the container kept a
static `mobile-collapsed` class. With no expand mechanism left, the
header-right stayed display:none on mobile, so the response-viewer eye
icon was unreachable even with "Response Viewer" enabled — desktop was
fine because the media-query rule doesn't apply there.
Restore the simple inline always-visible header-right layout (dev's
known-good state). The showResponseViewer setting still controls the
eye's --hidden marker class.
Verified on iPhone viewport: eye visible (26x26) with setting on, hidden
with setting off, tap opens the viewer; desktop eye unaffected.