Dropping the floor outright removed a guard. :host here was only display:block,
so an embed that gives the element no height leaves .gb{height:100%} resolving
against an auto-height parent and renders nothing — the collapse the floor was
there to prevent. The standalone leaf hides this, because it sizes the element
with position:fixed and inset:0; an arbitrary embed does not.
The floor belongs on :host, which is where every other plugin keeps it —
research-map at 320px, people-groups at 420px, big-picture at 480px. This plugin
was the one that put it on the inner root instead, and that is the whole bug: on
the host it guards a collapse while a shell that sizes its own pane can override
it from outside, whereas on .gb it could only push the element past its pane and
hand the host a second scrollbar across the tab strip.
The value is carried over unchanged rather than tuned while it moves, though
640px is the largest floor in the fleet and worth a second look on its own.
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