The gallery's startup thumbnail check runs one second after load. When that
second ended while the page was leaving (CI, WebKit: the workflow test
navigates from the gallery to the admin page), WebKit failed the new read
with "Fetch API cannot load ... due to access control checks." and
Playwright reported a page error.
Like the admin page (#290), the gallery now has a page lifetime that ends
on beforeunload and pagehide (and starts again on a back/forward restore).
The check starts no read once it has ended and passes it as the read's
signal. A page-clock workflow test that leaves before the second ends
failed on both events, in Chromium and WebKit, before this change.
Vito Sansevero
bac05711b9