We automatically refresh the page 'on the next navigation' whenever a
new version of the JS client is available. If the composer is open when
this happens then it will be closed and you'll have to reopen the draft.
In some circumstances, this refresh can also cause some composer content
to be lost.
This commit updates the auto-refresh logic so that it doesn't trigger
while the composer is open, and adds an acceptance test for the
behaviour.
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